Agreement INGV-DPC 2007-2009

Project S5 : “High-resolution multi-disciplinary monitoring of active fault test-site areas in Italy”

UR Reports - II phase

May 1st, 2009 – May 31st, 2010

Task1. Test site Alto Tiberina Fault (ATF). UR1 -INGV: Lauro Chiaraluce (CNT-INGV).

The works carried out and finalised over the past two years have been devoted to the foundation of the permanent Alto Tiberina Fault test site. During this period of time the INGV Airplane working group finalised the monitoring infrastructure composed of a dense network of co-located seismological and geodetic instruments. There was then a need to recover complementary information to turn on both the observing system and to immediately start planning its future implementation. The S5 project allowed us to provide many of these necessities.

With the Working Package 1 (Raffaele Di Stefano; CNT-INGV) we answered the question: how can we observe the seismicity pattern that characterises the activity of a normal fault system for a long period of time with the least manual work? That is why we set up a modular and semi-automatic procedure that goes from continuous waveforms to high resolution event location, computation of magnitude and focal mechanism. The process comprises independent codes that allow us to monitor with time a series of parameters such as network detection threshold versus the completeness of magnitude of our catalogues, the rate of seismic release, b-values and VP/VS ratio at single station and the level of noise. A final modulus analyses the generated datasets to produce maps and graphs for interpretation. The whole procedure runs on the on-purpose setup Linux machine. Results obtained in the project framework. The terrible occurrence of the L’Aquila earthquake in April 2009 forced us to implement, calibrate and test our procedure on the aftershock sequence. Examples of the result from automatic 1D locations and magnitude completeness are shown in the following two figures.

Figure 1.1: Map and set of vertical cross sections showing the outputs of the location 4 steps procedure run on the L’Aquila seismic sequence subset. These are all the events with ML≥1.9 present in the INGV National Network catalogue we picked also at the stations of the local and temporary networks.

The last column of Figure 1.1 shows the great enhancement we achieved in focusing the fault system geometry through the automatic detection and location of seismicity which hit the L’Aquila region. All the P- and S-wave arrival times catalogue have been generated by using a semi-automatic procedure: we did not hand pick a single seismogram. The great improvement in location resolution is mainly due to the homogeneity of the weighted scheme we were able to provide for the whole catalogue. The total machine time for the elaboration of 3000 events recorded at a mean of 50 three component seismic stations is ~3 days. Despite the need for a sometimes elaborated calibration procedure of the picking code, we believe the availability of this procedure represents a high innovation with regards to time consuming procedures.

Figure 1.2: MC versus time for two catalogues containing the seismicity occurred about 40 km far from the L’Aquila city from the 6th to the 16th of April, 2009.

The red line in Figure 1.2 represents the completeness versus time of the catalogue we generated by applying our triggering algorithm and location procedure on the continuous recordings of the permanent and local networks. A comparison is made with the INGV Iside catalogue, shown with a blue line. In this Figure we can appreciate the high performance of our automatic procedure that once the noise related to the mainshock occurrence (6th of April) decreases, the triggering-location modules are able to reach MC ~1.3. The availability of these modules will allow us to perform analysis of a very large dataset composed of tens of thousands of earthquakes opening new ways to look at seismicity patterns.

Problems and difficulties. As mentioned above we run our procedure on the 2009 L’Aquila sequence instead of testing and calibrating it on the test site data which is available from the beginning of 2010. This means that both the organisation of the data storage and results dissemination through dedicated web site pages were provided by the ING National Earthquakes Centre. Further on- line information will be available for information produced on the ATF. The dedicated web server is hosted on the same computer that performs all the daily analysis and the modules devoted to the synthesis of the results is a simple web page architecture builder written in Linux bash shell that daily rebuild web pages with updated maps and graphs for interpretation, based on the elaboration and analyses of the newly generated datasets.

With the Working Package 2 (Resp.: Luigi Improta; Roma1-INGV) we performed a high resolution seismic exploration survey aimed at obtaining reflectivity and VP shallow images to provide insights both on the shallow architecture of the Quaternary Tiber basin and the Alto Tiberina Fault (ATF) system, together with information to optimize the location of shallow drillings to install borehole seismometers planned in the framework of the Project MIUR AIRPLANE. Details on the survey design, data acquisition and processing are available in a technical report where we also describe Deliverables D2-D3. The first phase of research was devoted to the sites for surveying that could target both the structure of the Tiber basin and shallow splays of the ATF. Finding suitable survey sites was a challenging task because of significant logistic and environmental difficulties. We investigated the sector of the basin between Umbertide and Perugia, about 20 km long, by analyzing aerial photos, geologic maps, industry seismic reflection profiles and by carrying out field surveys (Figure 2.1).

Figure 2.1. Structural map of the Tiber basin with outlined the traces of commercial reflection profiles (grey lines) and the area of the seismic experiment (red box). The blue line is the commercial reflection profile L7 located 3km to the south of the survey area, which provides information on the large scale structure of the basin and ATF (after Mirabella et al., 2004).

As a result, we identified a suitable area located just 3 km to the north of a commercial profile, where we collected two HR SW-trending seismic profiles that extend from the central portion of the basin to the western and eastern ridges (Line A and Line B in Figure 2.2).

Figure 2.2. Simplified geologic map of the investigated sector of the basin, with outlined the two acquired HR profiles (A and B).

The total length of Line A and Line B is 1635 and 2050 m, respectively. Data were acquired with a dense, wide-aperture geometry. A high-resolution Vibroseis source was recorded by a geophone spreading 835 m long. Source and receiver spacing was 10 and 5 m. This geometry allowed the simultaneous collection of both multifold, common-mid-point, reflection data and dense refraction data. Overall, common shot gathers display a good signal to noise ratio. First arrivals are clear even for far offset traces, while most of the record sections show high- frequency near-vertical reflections and large amplitude, low-frequency wide-angle reflections.

Results obtained in the project framework. Seismic imaging aimed at defining HR reflectivity images of the sub-surface by standard CDP processing of reflection data, complemented by P-wave velocity images obtained by a refraction multiscale tomography. The two seismic stack sections show interpretable events down to 0.4 s TWT corresponding to 400-500 m depth. The western Line (A) shows coherent and laterally continuous reflectors, which define the internal geometry of the Quaternary continental infill along the western side of the basin (Figure 2.3). A noticeable result is the detection of an eastward dipping extensional fault along the western hill-slope, which did not appear in published geologic maps. This structure is interpreted as a high-angle synthetic splay of the low-angle ATF that can be traced along the entire seismic profile down to 0.4 s following gently eastward dipping subtle reflectors. The tilting and growth of fluvio- lacustrine strata towards this high-angle fault evidence its syn-sedimentary activity, while truncation of near-surface reflectors (<30-50 m depth) referable to Late-Pleistocene–Holocene terraced deposits documents recent slip along this structure.

Figure 2.3. Stack section with schematic line drawing of Line A. The red dashed Line A. line outlines the low dipping ATF. Note the synthetic high angle extensional splay positioned at 600 m.

The eastern Line (B) well defines the westward thickening of the Tiber basin (Figure 2.4). West-dipping fluvio-lacustrine Quaternary deposits on-lap onto an articulated substratum, which rapidly rise to only 0.15 s (~150 m depth) beneath the central portion of the profile. This feature is confirmed by VP models obtained by multiscale refraction tomography, which consistently image a broad high-VP (3.0-3.4 km/s) anti-formal structure. This structure can be interpreted as the prolongation of the fold developed within Miocene rocks, which crops out ~1 km to the north of the profile. The substratum and overlying Lower-Middle Pleistocene fluvio-lacustrine deposits appears truncated by a westward dipping fault below the eastern side of the profile. This structure could represent an antithetic extensional splay of the ATF system.

Figure 2.4. Stack section with schematic line drawing of Line B. Note the articulated geometry of the pre- Quaternary sub-stratum (brown line). And the SW-dipping extensional structure on the eastern side.

The analysis of the acquired data will allow us to greatly improve the imaging resolution of the shallower portion of the system complementarily to the industrial reflection profiles quite poor in the upper 0.2-0.4 s TWT. This study fills the gap existing between commercial reflection profiles and surface geologic data. In particular, the high-resolution stack sections give constraints on the shallow architecture of the basin and extensional fault system, which are relevant for a better understanding of: (1) the stratigraphy of the continental deposits infilling this sector of the basin, (2) the kinematic interaction between the Alto Tiberina fault and secondary splays, (3) the long-term and recent evolution of this sector of the basin. Although we investigate a small portion of the Tiber basin, our high-resolution shallow images can be useful to locally assess the long-term and short-term extension rates of the ATF obtained by oil industry/morpho-structural data (w.p. 1.4 and w.p. 1.5) and geodetic measurements (w.p. 1.3), respectively. However, the knowledge of the geometry and VP structure of the basin will be valuable to assess local seismic response for this portion of the basin. Finally, our investigations suggest that the anti-formal structure detected along the Line B consisting of high-VP flysch deposits buried at ~150 m depth below Quaternary clastics, can be a suitable target for shallow drillings to install borehole seismometers planned within AIRPLANE Project.

Problems and difficulties. Unfavorable logistic and environmental conditions posed significant difficulties to the identification of potential sites for seismic surveying. In particular, the Tiber river, a railway and a highway parallel the valley, thus acting as barriers to seismic profiling across the basin. As a consequence, we collected to two distinct HR seismic profiles extending from both sides of the basin to the mountain fronts. Furthermore, we did not acquire VHR data along shorter collocated profiles because the use explosive sources were not permitted by landowners. Moreover, many people involved in this project contemporaneously contributed to the planning and realization of the active seismic experiments in the L’Aquila area in 2010, resulting in a light delay in the profiles interpretation.

With the Working Package 3 (Resp.: Nicola D’Agostino; CNT-INGV) all the available continuous GPS data collected in the interval 1994-2010.12 were collected and analysed. The velocities relative to stable Eurasia are presented for the 57 stations with ages larger than 2.5 years. The GPS data were processed using the GIPSY software (Zumberge et al., 1997), as part of a regional, ambiguity-resolved network solution computed by the Ambizap software (Blewitt, 2008; D'Anastasio et al., 2008), with station velocities and their uncertainties determined using the CATS software (Williams, 2003). To interpret the GPS velocities in terms of regional tectonics, we present the velocities relative to the Tyrrhenian coastal region. This choice provides the most appropriate framework to study the extension in the Apennines and defines a reference frame that meets a condition of no internal deformation at the level of GPS velocity uncertainties (WRMS, 0.33 mm/yr East; 0.32 mm/yr North).

Results obtained in the project framework. The retrieved geodetic velocity field showed in Figure 3.1 (top) illustrates a relatively simple pattern of crustal extension in which Tyrrhenian-fixed velocities southwest of the Apennines divide are not statistically significant, whereas crossing the drainage divide the velocities progressively align with the north-eastward motion of the Adriatic micro-plate relative to the Tyrrhenian coastal region. The observed crustal extension is not uniformly accommodated across the Apennines, but deformation appears to concentrate across the alignment of historical and recent seismic events. The velocity profile shows that the relative motion between the Adriatic and Tyrrhenian coast is accommodated in a rather large area. The increase of north-eastward velocity occurs well beyond the Alto-Tiberina Valley (vertical arrows in Figure 3.1, bottom) and overall extension is about 3 mm/yr. These results do not support the hypothesis that crustal extension is exclusively accommodated by aseismic slip at shallow depth along the Alto Tiberina Valley fault system as recently suggested by Hreinsdóttir and Bennett (2009). Figure 3.2 shows the spatial distribution of the tectonic strain rate. The strain rate was obtained following the methodology outlined in D'Agostino et al.(2008) in which the horizontal velocities are interpolated with a spline with tension (Wessel and Smith, 1999). The continuous functions are then spatially derived to obtain the velocity gradients. From the tensor of the velocity gradients the complete strain-rate tensor was calculated on a regular 0.1°x0.1° grid and represented in Figure 3.2 as the tensor second invariant (colour scale) or by means of its principal axes (converging and diverging arrows). The distribution of strain rate shows a continuous band of deformation running along the crest of the Apennines coinciding with the maximum release of historical and instrumental seismicity. The geodetic strain rate has been converted in geodetic moment rate using the expression given in Ward (1994) and using a constant value of the seismogenic thickness (10 km) and a value of 3.3e10 Nm for the rigidity. These datasets are included as deliverables (see below). The geodetic moment rate allows to evaluate the rate at which secular tectonic deformation accumulates, and the value of elastic deformation stored since the last seismic events and eventually available in forms of future seismic events. This information is potentially very useful as additional data in seismic hazard assessment practices.

Figure 3.1. Top: GPS velocity field of the Northern Apennines. The vectors show velocities relative to a reference frame obtained by minimization of the horizontal velocities of GPS stations on the Tyrrhenian coast. Ellipses show velocity uncertainties at 95% confidence interval. Black arrows are the velocities calculated from the interpolation algorithm. The box encloses the swath used to project the horizontal velocities showed in the section. Bottom: blue dashed line is the projection of the horizontal velocity calculated by the interpolation algorithm.

Figure 3.2. Strain rate calculated from the spatial gradients of the interpolated velocity field. The colour scales to the value of the second invariant of the strain rate tensor. Diverging and converging arrows show the principal axes of the strain rate tensor.

Deliverables.

# Description Type Authors Restrictions Contact person Releva nce D1 Standard modular Applicat Di Stefano R., L. Any use of the [email protected] High automatic procedures ions Valoroso, D. scientific data for the management (e.g. Piccinini, L. included in and analysis of a codes). Chiaraluce, P. De the continuous seismic Gori. deliverables data stream. should be defined in agreement with the coordinator of the WP. D2 2 HR and VHR stack Profiles. L. Improta, P. P. Any use of the [email protected] High sections and VP Bruno, D. De scientific data images of the Tiber Rosa, S. included in basin (~500 m deep) Pierdominici, F. the and of the shallow Varriale, F. deliverables fault zones (100-150 Villani, A. should be m deep) belonging to Castiello. defined in western splays of the agreement ATF. with the coordinator of the WP. D3 Definition of an Lat. L. Improta, P. P. Any use of the [email protected] Low optimal site for a 200 Lon. Bruno, D. De scientific data m deep drilling in the Rosa, S. included in Tiber basin to install Pierdominici, F. the borehole Varriale, F. deliverables seismometers. Villani, A. should be Castiello. defined in agreement with the coordinator of the WP. D4 Time series of GPS Files N. D’Agostino, S. Any use of the [email protected] Low stations at ATF test Mantenuto, E. scientific data site in the ITRF2005 D’Anastasio, D. included in reference frame. GPS Cheloni. the velocity field in the deliverables ITRF2005 and should be Eurasian reference defined in frames. agreement with the coordinator of the WP. D5 Map of strain rate Map N. D’Agostino, S. Any use of the [email protected] High and geodetic moment Mantenuto, E. scientific data rate at ATF test site. D’Anastasio, D. included in Cheloni. the deliverables should be defined in agreement with the coordinator of the WP.

Publications.

Oral presentations: Chiaraluce L., R. Di Stefano, D. Piccinini and L. Valoroso. The 2009 L'Aquila seismic sequence (Central Italy): fault system geometry and kinematics. European Geosciences Union (EGU) General Assembly. Vienna, Maggio 2010.

F. Aldersons, L. Chiaraluce, R. Di Stefano, D. Piccinini and L. Valoroso. Automatic Detection, and P- and S-wave Picking Algorithm: an application to the 2009 L'Aquila (Central Italy) earthquake sequence, Fall Meeting of American Geophysical Union (AGU). San Francisco, Dicembre 2009.

Valoroso L. and the L’Aquila 2009 Mobile Network Working Group. The 2009 L'Aquila seismic sequence (Central Italy): fault system geometry and kinematics, Fall Meeting of American Geophysical Union (AGU). San Francisco, Dicembre 2009.

Chiaraluce L. and the L’Aquila 2009 Mobile Network Working Group. The contribution of the INGV mobile network in monitoring the 2009 L’Aquila (MW 6.3) seismic sequence (Central Italy). Active tectonic studies and earthquake hazard assessment in Syria and neighbouring Countries. Damasco, Novembre 2009.

Chiaraluce L., C. Chiarabba, P. De Gori, R. Di Stefano, L. Improta, D. Piccinini e L. Valoroso. The 2009 L’Aquila Seismic Sequence (Central Apennines): Fault System Geometry and Kinematics. Congresso della SOCIETÀ GEOLOGIA ITALIANA. Rimini, Settembre 2009.

D'Anastasio, E., D'Agostino, N., Avallone, A., and Blewitt G., 2008, Present-day kinematics of the central Mediterranean plate boundary region from large GPS network analysis using the Ambizap algorithm: Eos Trans. AGU 89 (53), Fall Meet. Suppl., Abstract G21A-0673.

Publications: D'Agostino N., Mantenuto S, D'Anastasio E, Avallone A, Barchi M., Collettini C., Radicioni F., Stoppini C and Fastellini G. (2009). Contemporary crustal extension in the Umbria- Marche Apennines from regional CGPS networks and comparison between geodetic and seismic deformation. Tectonophysics,v.476 (1-2,) p. 3-12, doi:10.1016/j.tecto.2008.09.033.

Chiaraluce L., C. Chiarabba, P. De Gori, R. Di Stefano, L. Improta, D. Piccinini, A. Schlagenhauf, P. Traversa, L. Valoroso and C. Voisin. The April 2009 L’Aquila (Central Italy) Seismic Sequence. Submitted to BGTA.

Task1. Test site Alto Tiberina Fault (ATF) UR2-UniPG: Massimiliano R. Barchi

Activity of UR The activity of the Perugia UR is subdivided into two sub-projects, dedicated to the subsurface geology (wp 1.4 resp. F. Mirabella) and to the surface geology and geomorphology (wp 1.5 resp. M. Barchi). Wp 1.4 provides a detailed reconstruction at depth of the Altotiberina fault geometry and of the most significant stratigraphic markers; 3 sequentially restored geological sections are also provided. Wp 1.5 define the geological and geomorphological evolution of the Tiber Valley, between Perugia and Città di Castello, providing a new cartography carried out with homogeneous criteria.

WP 1.4 Upper crustal structure and tectonic evolution of ATF The activity of the wp 1.4 was focussed on the geological reconstruction of the subsurface of the Altotiberina normal fault (ATF) and on the sequential restoration of 3 geological sections across the ATF. The UniPg people involved in the wp are F. Mirabella, M. Barchi and A. Lupattelli (PhD project). In order to improve the surface geology data, F. Brozzetti (University of Chieti) was also involved for his expertise of the stratigraphic and structural setting of the study area. His contribute was especially aimed at the construction of detailed geological cross-sections at shallow (< 1 km) structural level, to be integrated with the seismic reflection data. In this project we re-considered all surface and subsurface data both at ATF foot-wall and hanging- wall. The data consist of surface geological maps (1:10.000, 1:25.000, 1:100.000 scale), and subsurface data (boreholes and commercial seismic data). Surface and subsurface data, projected into a common geographical reference system with GIS tools, were loaded into the MoveTM package to perform the depth conversion and sequential balancing of the geological sections. The sequential restoration and balancing was addressed along 3 sections (L1, L3 and L5, deliverable 5) which cross the ATF. The interpretation of these sections is calibrated by three boreholes, S.Donato1, M.Civitello1 and Perugia2. A longitudinal (tie) section was also elaborated, integrating subsurface data along the trace of a significant seismic profile (L6, deliverable 5). The interval velocities adopted for the depth conversion of the seismic profiles are summarized in table 1. The adopted Vp were derived from direct measurements performed by Agip while drilling the boreholes in the study area, compared with other boreholes drilled through the same lithological units in adjacent areas. These values are consistent with literature data.

Seismo-stratigraphic Units Interval P-wave velocity (m/s) Continental deposits (Late Pliocene-Quaternary) 2000 Tuscany Turbidites (Oligocene- Early Miocene) 4300 Umbria Turbidites (Middle-Late Miocene) 4000 Carbonatic multilayer (Jurassic-early Miocene) 5600 Evaporites (Late Triassic) 6100 Basement s.l. 5100 Table 1: Seismic interval velocities (Vp) adopted for the depth-conversion of the seismic profiles

Section L1 is a re-interpretation of the Crop-03 profile. The geological structure at the ATF foot- wall was interpreted, using a set of seismic profiles (west of Citta' di Castello), nor available in the previously published works: the new seismic lines constrain the depth of the Umbria Marche carbonates below the siliciclastic rocks exposed at the surface. Section L3 crosses the ATF extensional system and its trace is located close to the S.Donato1 and M.Civitello1 wells. Section L5 crosses the southern part of the study area, close to the foot-wall structural culmination of M.Malbe and to the Perugia2 well. The sections show the present-day geological setting of the ATF extensional system consisting of three main normal faults, from West to East: the SW-dipping Corciano fault, the ENE-dipping Altotiberina Fault (ATF) and the SW-dipping Gubbio fault. The combined effect of the Corciano fault and of the ATF is responsible for the exhumation of late Triassic rocks (Anidriti di Burano Fm) at the ATF footwall in sections L3 and L5. The easternmost segment of the ATF borders the Tiber Valley basin, infilled with up to 1 km of late Pliocene (?) - Quaternary sediments. The displacement along the major normal faults was sequentially restored. We applied two different balancing procedures, based on 90° and 70° inclined shear vectors respectively: the 70° shear vector results into slightly larger values of horizontal extension. The resulting total amount of extension is between 4.6 and 5.2 km for section L1, between 8.6 and 9.7 for section L3 and between 6.5 and 7.6 for section L5. These values are plotted in figure 1. On the plot we also drew the extension values evaluated along a further section (L2) located between L1 and L3. The plot shows that the ATF reaches a maximum value of extension (about 9.5 km) in correspondence of section L3, progressively decreasing both toward NW and SE. Considering the ages of the sediments infilling the basins and the regional framework, the onset of extensional deformation can be fixed at about 3 Ma. On this basis we estimate a long-term extension rate comprised between of 2.8 and 3.2 mm/yr. Such value is consistent with the present- day extension rates inferred from geodesy (2.7 mm/yr – wp 1.3) suggesting an almost uniform deformation rate in the last 3 Ma. The sequential restoration also shows: i) the kinematic interaction between the ATF and the SW- dipping (Gubbio and Corciano) normal faults ii) the influence of the staircase geometry of the ATF on the onset and evolution of the Tiber basin at its hanging-wall; iii) the pre-extensional geometry of the compressional structures. Using the entire data-set of seismic profiles, we produced isochronous maps of the ATF and of the top Basement (base of the sedimentary cover). Using the interval velocities (table 1), we converted the seismic data into depth and produced the isobath maps of the ATF and top Basement (deliverable 6).

Figure 1: Long-term (i.e. total) extension and throw distribution along the ATF from NW to SE (along section L6) showing the bell-like distribution of the offset along the fault strike. The points of measure correspond to L1, L2, L3 and L5 sections from NW to SE.

The isobath map of the ATF shows that the fault is characterized by a pronounced staircase trajectory with dips varying form about 15° to 30°. The fault is also characterized by some longitudinal bends, due to attitude variations along its strike. The irregularities of the ATF surface (both along strike and along dip) might be of interest for the evaluation of the seismic hazard related to the ATF (fault segmentation). The top Basement isobath map (deliverable 6) shows the two main thrusts affecting the basement, that progressively deepens towards ENE. The central part of the map is blank and corresponds to the area where the ATF displaces this marker, providing an along-strike image of the ATF location at relatively deep structural level.

WP 1.5 Tectonic evolution of the Upper Tiber Valley, from Perugia to Sansepolcro The activity of wp 1.5 was focussed on the geomorphological survey and aerial photograph interpretation of the Quaternary deposits of the high Tiber Valley from San Sepolcro to Perugia. An interdisciplinary team (structural geology, Quaternary stratigraphy and sedimentology, geomorphology) was involved in this wp, including M. Barchi (UniPg), L. Melelli (Unipg), F. Pazzaglia (UniPg), S. Pucci (INGV), and L. Saccucci (PhD project). Further support to the project was offered by: L. Sagnotti, F. Speranza and M. Maffione (INGV), who made palaeomagnetic analysis of a section of the lacustrine clays; and M. Soligo and P. Tuccimei (Lab UniRoma3), who made radiometric dating of a sample of calcareous tufas. Extensive 1:10,000-scale geological and geomorphological mapping along the Upper Tiber Valley, has been carried out, focussed on the continental deposits infilling the Tiber basin. We started from the existing geological maps, produced in the framework of previous national (CARG) and/or regional (Regione Umbria) projects. The field work was aimed at producing an integrated and homogeneous stratigraphic scheme (deliverable 7) of the continental deposits (< 1.8 MA in age), characterized also from a sedimentological and structural point of view. The map (deliverable 7) was integrated with observations derived from 1:33,000 scale aerial photographs (GAI) and 10 m and 90 m resolution Digital Elevation Models (DEMs). Within the high Tiber valley, we distinguish three sub-basins (namely, North to South: Sansepolcro, Umbertide and Ponte Pattoli basins), separated by thresholds. The genesis and evolution of these sub-basins is driven to the activity of the recentmost (~2 Ma) splays of the ATF. Along the Tiber valley, recent alluvial deposits (late Pleistocene-Holocene) unconformably overlay a complex fluvio-lacustrine Pleistocene succession (“lago Tiberino” succession). The latter consists of three depositional cycles, bottom to top: the Fighille Unit (early Pleistocene), with a prevalent clay sedimentation; the Citerna Unit (early-middle Pleistocene), with prevalent conglomeratic sediments and some sandy interbodies; the uppermost cycle (Valliano and Ascagnano Units, middle-late Pleistocene) with heterogenic deposits restricted to narrow areas. Dating the continental deposits is not an easy task. The Fighille Unit is dated by mammal faunas (F.U. Tasso) and preliminary paleomagnetic measurements (reverse chrono, possibly Matuyama zone). The Citerna Unit is dated by two very rich mammal faunas (F.U. Colle Curti and lower Galerian post Colle Curti), founded in the Promano quarry (Umbertide basin). The Ascagnano Units, pertaining to the third cycle, is characterized by calcareous tufas (stromatolitic, phytohermal and phytoclastic tufas) probably deposited in a river environment: a U/Th dating (82 ± 7 ka), coherent with a warm period (OIS 5a), has been made within this unit. We also mapped the distribution of the river terraces along the Tiber valley (figure 2). The data were plotted into a set of closely spaced topographic transects: due to the outcrops condition, the widespread extensive cultivations and the paucity of control points on the terraces straths, we plotted the terraces treads on the topographic transects. We recognized at least two orders of terraces along the river and sparse older palaeo-surfaces at higher elevations. The presence of these terraces is not uniformly distributed along the Tiber valley. Figure 2: Schematic distribution of the alluvial deposits and fluvial terraces along the Tiber valley from Sansepolcro to Perugia (right) and synthesis of the local uplift-subsidence relationships along the river (left).

Figure 3: Plot of the river terraces elevation mepped along the Tiber valley longitudinal profile form Città di Castello to Perugia.

In the northern Sansepolcro sub-basin, the valley is characterized by the overall absence of fluvial terraces: the only terrace (San Leo) is exhumed at the footwall of an active, E-dipping normal fault, bordering the Anghiari ridge towards the ENE (figure 2 and deliverable 7). Along the other two sub-basins, south of Città di Castello, two orders of fluvial terraces were recognized: the plot of figure 3 shows that the elevation and distribution of these terraces is not regular, marking significant longitudinal variations of the incision operated by the Tiber river. These variations can be interpreted as the results of the interference between two opposite driving mechanisms, the regional uplift (about 0.5 mm/yr) and the local subsidence of faulted blocks (figure 2, left). Climatic/eustatic changes also affected the evolution of the drainage system. Our results indicate that the recent (Late Pleistocene to Holocene) evolution of Sansepolcro basin is dominated by local subsidence (i.e. tectonics), while in the southern basins the faults activity is less vigourous, hence the uplift dominates promoting river incision. This result is reinforced by the observed thickness of the recent alluvium (up to 150 m) infilling the Sansepolcro basin, much larger than in the other basins. The distribution of the historical and instrumental seismicity also indicated a stronger tectonic activity in the northernmost portion of the High Tiber Valley. The Perugia UR also contributed to the geodetic survey of the study area, through a sub-contractor in the first year of activity. The sub-contractor (F. Radicioni and A. Stoppini at the Civil and Environmental Engineering Department of the University of Perugia) performed the acquisition and maintenance of the local GPS network of Umbria. Their activity was described in the scientific report of the first year of the project. 2.1 Deliverables The deliverables are: D6 three balanced cross sections (completed at 100%) and longitudinal section (completed at 100%) D7ATF and top basement isobath maps (completed at 100%). D8 a geological and geomorphological map of the High Tiber Valley from Perugia to Città di Castello (completed at 100%)

# Description Type Authors Restrictions Contact person Relevance

D6 Balanced sections Tables Mirabella F., Authorization Mirabella F. Balanced sections across the ATF Barchi by the authors mirabell@unipg. are important to M.R.Brozzetti F.,, is requested it define long term Barchi M. extension rate of mbarchi@unipg. ATF it

D7 Isobath maps of Maps Mirabella F., Authorization Mirabella F. In a 3D image the the ATF and of Barchi M.R., by the authors mirabell@unipg. ATF images dip the top of Brozzetti F., is requested it variations which basement Lupattelli A. Barchi M. can affect the fault mbarchi@unipg. segmentation it D8 Geological and Maps Barchi M., Authorization Mirabella F. Different evolution geomorphologic Melelli L., by the authors mirabell@unipg. of the basin is al map of the Pazzaglia F., is it found along the high Tiber Pucci S., requested Barchi M. High Tiber Valley valley Saccucci L. mbarchi@unipg. it

2.1 Problems and difficulties - The Vp values derived by direct measures within the boreholes define a subsurface velocity model which is not always comparable with those commonly used for earthquake location and passive seismic tomography in the same region. This point should be discussed by the scientific community. - The construction of the isobath maps of the ATF splay was hampered by the scarce longitudinal continuity of these faults, compared to the spacing the available seismic profiles. In the map the ATF is assumed to be a continuous surface, but this point is not completely constrained by the subsurface data. - The dating of the continental deposits is a very difficult task, that is necessary for a reliable reconstruction of the tectono-sedimentary history of the basin. This task would require a dedicated project, integrating traditional (e.g. mammal faunas) and innovative (palaoemagnetic, absolute dating) techniques. 2.2 Key publications Barchi M., Lupattelli A. and Mirabella F. 2008. "Balanced cross-sections across a low-angle normal fault in the Northern Apennines of Italy". Congresso della Societa' Geologica Italiana, September 15-17 2008, Sassari (Italy). Barchi M., Mirabella F., Chiaraluce L., Cocco M. and Montone P. 2008. "An active low-angle normal fault in the Northern Apennines (Italy): a possible site for ICDP drilling". 33rd International Geological Congress (IGC), Oslo August 6-14th 2008 (Norway). D’Agostino N., Mantenuto S., D’Anastasio E., Avallone A., Selvaggi G., Barchi M., Collettini C., Radicioni F., Stoppini A., Fastellini G. 2009. “Contemporary crustal extension in the Umbria- Marche Apennines from regional CGPS networks and comparison between geodetic and seismic deformation”. Tectonophysics, 476(1-2), 3-12, doi: 10.1016/j.tecto.2008.09.033. ISSN 0040-1951. Mirabella F., Barchi M., Brozzetti F. and Lupattelli A. 2009. “Balanced cross-sections across a low angle normal fault in the northern Apennines of Italy” settimo forum italiano di Scienze della Terra (FIST), Rimini 07-11 Settembre 2009. Mirabella F., Barchi M.R., Brozzetti F. and Lupattelli A. 2009. "UR 2 - WP 1.4 di S5 Upper crust structure and tectonic evolution of the Altotiberina normal fault (central Italy)" Agreement INGV-DPC 2007-2009 Annual Meeting of the Seismological Projects, Roma 19-21 Ottobre 2009. Barchi M.R., Melelli L, Pazzaglia F., Pucci S., Saccucci L. 2009. "UR 2 - WP1.5 di S5 Tectonic evolution of the Tiber Valley between Perugia and Città di Castello". Agreement INGV-DPC 2007-2009 Annual Meeting of the Seismological Projects, Roma 19-21 Ottobre 2009. Mirabella F., Barchi M., Brozzetti F., Lupattelli A., Melelli L., Saccucci L., Pazzaglia F. and Pucci S. 2010. "Morphotectonic evolution of a Quaternary basin driven by a segmented low-angle extensional system" Rendiconti della Società Geologica Italiana. in press Mirabella F., Brozzetti F., Lupattelli A., Barchi M. 2010. "Tectonic evolution of a low-angle extensional system in the Northern Apennines from restored cross-sections". In preparation. Section 2: Report on the project S5 Task2 Messina Strait

by UR 03 Margheriti L. and D’Anna G.

The general goal of the UR03 was to contribute to the “Messina 1908-2008” project (Margheriti et al 2008) in the years of the centennial of the 1908 earthquake (Mw=7.1), for the understanding of the regional kinematics in which the extension processes occur in the Messina Strait.

In S5 project, we deployed five Ocean Bottom Seismometers (OBS) that integrate the on-land seismic monitoring system; we promoted new geodetic campaign measurements; and finally developed and applied innovative methodologies to characterize the strain-field in the Messina Strait and in the surrounding Calabro-Peloritani arc. The UR03 research planned by UR03 were partially achieved and are presented in the following. Some of the activities were delayed for technical problems and one of the deliverables was not achieved because, the occurrence of the L’Aquila earthquake on April 2009 introduced a new scientific priority in the working program of the INGV staff. On the other hand the INGV emergency management during the L’Aqulila seismic sequence benefited of the work done in S5; specifically the procedures developed by UR03 for building a seismological SEED data archive (see w.p. 4.2 in Task4) and for the evaluation of seismic anisotropy ( see w.p. 4.2 in Task4) were applied.

Results

WP 2.1 Ocean Bottom Seismographs deployment and test (Giuseppe D’Anna – Giorgio Mangano, INGV- CNT)

In a region were most of the surface is occupied by sea (Fig 1) the OBS recordings integrated to the data of the mobile and permanent stations on-land can improve the detection capability of the seismic network and the quality of the locations of the seismicity in the area (see report S5 phase I). This is the first INGV seismic passive experiment in Italy in which submarine seismic stations are deployed together with on-land stations. The test of the OBS stations, developed by the Gibilmanna Lab, is an important technological contribute of the project for the development of a new OBS “B version” which can be successfully used in the future for monitoring the Italian territory. Moreover in the frame of S5 we realized the implementation of a bidirectional communication system (new electronic boards for acquisition and communication). The first OBS campaign is described in the PhaseI report.

Fig. 1 – map of deployment points - II° campaign S5 The second OBS campaign was delayed five months respect to the plan of the project, and started this February. Five OBS”B”/H were deployed see locations in Fig. 1 and coordinates and depths are in Table 1. Their recovery is scheduled in October 2010. They are equipped with the new seismic sensor Guralp CMG40T-OBS (60 sec.-100Hz); four of them have a DPG (Differential Pressure Gauge, 500 sec - 2 Hz) to record pressure signals, while the OBS deployed on the top of Marsili Volcano has a temperature sensor and a hydrophone (100 sec-8 kHz) to record high frequency signals generated from submarine hydrothermal fluids or gas. Table 1: coordinates and depth of the deployment points - II° campaign S5

OBS DATE UTC TIME LATITUDE LONGITUDE DEPTH

A4 05/02/2010 18.07.34 38° 40,008 N 15° 27,006 E 1409 MT

A2 06/02/2010 0.37.41 38° 52,996 N 14° 20,089 E 1510 MT

A5 14/02/2010 9.42.53 39° 01,971 N 14° 47,115 E 3315 MT

A7 14/02/2010 14.34.00 39° 16,401 N 14° 23,601 E 791 MT

A6 14/02/2010 17.51.00 39° 29,997 N 13° 59,991 E 1502 MT

The instrument placed on the Marsili Volcano (Fig. 2) follows, after three years and a half, the prototype test of the first OBS / H carried out in the summer of 2006. The deployment area is a plateau of about 150 x 200 meters at a depth of 790 meters near the summit area located at about a Mile towards N / E.

During that campaign, lasting just nine days, more than 1000 events were recorded: 900 VTB events (Volcano Tectonic type B) and 90 high frequency events linked with intense hydrothermal activity.

The new instrument OBS / H, version B (Fig. 3), has been completed and passed the first laboratory test. The new electronic boards for data acquisition and communication, developed by the Gibilmanna Fig. 2 – deployment OBS/H on the Marsili Volcano OBS Lab and the Experimental Seismology Laboratory – CNT, were tested in laboratory. The final test of the new instrumentation, at sea, initially scheduled during the deployment

2006-07-20, M 2.7, Mar Ionio

1 campaign, due to limited 0.5 ship time available in

mVolts 0

-0.5 February 2010, will be

-1

9:06:00.000 9:06:20.000 9:06:40.000 9:07:00.000 9:07:20.000 9:07:40.000 9:08:00.000 9:08:20.000 9:08:40.000 9:09:00.000 9:09:20.000 Real Time carried out during the Acoustic recovery campaign link scheduled in October 2010. This is the first important step to become able to retrieve OBS data without recovering the instrument.

Fig. 3 – OBSH/B version completed in laboratory, new acquisition and communication boards are installed in the OBS”B”

WP 2.2 Integrated seismic data bank and refined earthquake location to define seismogenetic structures. Milena Moretti | CNT- INGV

Main goal of this working package is the creation of a waveform archive that collect, in a uniform format (SEED - Standard for the Exchange of Earthquake Data) recordings of all the available seismic stations present in the the Calabro - Peloritana area across the Messina Strait. The passive seismic experiment has been carried out from October 18, 2007 to January 31, 2010 (Figure 4). We were supposed to locate the earthquakes recorded in the Messina area during the project. The new data can be extremely useful to obtain refined location that help to better define seismogenic structures inside the Messina Strait and in the surrounding region especially in the Tyrrhenian and Ionian sea. We have evaluated on 8 events the improvement introduced by the use of OBS and of the temporary stations on earthquakes location (see deliverable D12 phase I). We did not determine new earthquakes locations (deliverable D12) and so we did not verify if the new network is lowering the detection threshold. This deliverable was not achieved because, the occurrence of the L’Aquila earthquake on April 2009 focused for the last year the attention of the INGV staff involved in this working package and we are only now starting to work on the Messina data.

Fig. 4 – map of the available seismic stations in the region

The SEED data archive is the integration of continuous recordings provided by temporary deployments (15 seismic station on land and 5 OBS on sea) and permanent networks (INGV Italian Seismic Network, MedNet - Mediterranean Very Broadband Seismographic and Peloritani Local network). It can be retrieved at http://dpc-s5.rm.ingv.it/en/Database-MessinaFault.html and it is distributed trough EIDA, European Integrated Data Archive based on ArcLink (developed by Geofon, GFZ). The site allows complete access to both permanent and temporary station data.

The continuous OBS waveform data is temporarily available in miniSEED at ftp://ftp.ingv.it/pro/s5-data/ . Data will be merged in the integrated archive as soon as the meta data information is converted to SEED data format (dataless).

One of the most valuable results achieved during the work on S5 project is the implementation of a new temporary network data management that allows the integration in EIDA of the tempory deployment together with all other seismological data produced by INGV. This archive is the first example in Italy of complete integration of permanent networks, temporary deployments and OBS data that is becoming now a standard for INGV seismic experiment.

Figure 5 – Temporary seismic network data availability. The plot shows the “Start”, the “Stop” and all data gaps (“FAT error” caused by a wrong CF formatting; “rottura HD” caused by an Hard Disk failure; “baco GPS” caused by a bug in some GPS units firmware; “Int. A/C” caused by the switch off of the mains; “Furto” the station was stolen; “Incendio” the station was destroyed by a large fire). The light red box indicates the period of deposition of the OBS (July 15, 2007 – November 8, 2007).

WP 2.3 Seismic Anisotropy (Davide Piccinini RM1, INGV)

The study of seismic anisotropy in the crust and uppermost mantle help in defining the deformation field of the medium sampled by the seismic waves. To estimate the anisotropic parameters in the crust we investigate shear wave splitting phenomena (the analog of birefringence in optics). Seismic anisotropy is an almost ubiquitous property of the earth, the shear wave splitting is the most unambiguous indicator of anisotropy but the automatic estimation of the splitting parameters presents difficulties because the effect of the anisotropy on the seismogram is a second order effect not very easily detectable. In particular the anisotropic parameters in the crust individuate the fracture field geometries connected with the active stress field, and might be sensible to variations of stress contributing to define the strain field of the region from a seismological point of view.

Our objective was to develop a semi-automatic code able to evaluate the anisotropy of S waves and to apply it to the crustal earthquakes for characterizing the deformation and fracture field of the crust. We were supposed to apply this technique to the earthquakes recorded in the Messina area during the project.

The first step of our work was successful and focused on building a semi-automatic procedure analysing near real time seismic waveforms in order to estimate the deformation and fracture field of the upper crust. During the first year of the project individual programming skills were exploited refining two different codes with independent approaches. During this phase we perform some tests to validate the codes, and get comparable results (Val D’Agri). In the second year we realize the fine tuning of the semi-automatic code called ANISOMAT+. The code (deliverable D13) is now able to retrieve the anisotropy parameters of S waves for each events located from the network using a simple, fast and robust approach based on the cross-correlation of the two horizontal traces. The application of the code to the earthquakes recorded in the Messina area during the project was not achieved because we did not received the locations from w.p. 2.2, but we did apply our code to other datasets (Table 2).In Fig 6 are presented results for the test site of S5 Task1: The ATF area( see deliverable D13) and earthquakes recorded during L’Aquila seismic sequence at 3 stations (the test site of S5 Task4 WP 4.3).

We found in general good agreement of the average splitting parameters with the stress field of the analyzed regions (fast direction perpendicular to the Shmin). We observe significant spatial variations of the anisotropic parameters and we are investigating the relation between the occurrence of seismicity and the variations in time of the anisotropic parameters in the crust

Test Site Application to Val D’Agri to build and tune the Pastori M., Piccinini D., “Messin ANISOMAT+ code Margheriti L., Bianco a Strait” Application to deep events located in the Calabrian arc to F., Zaccarelli L., tune the ANISOMAT+ code in the area of interest Baccheschi P.. Test Site A first preliminary map of fracture field defined through Pastori M., Piccinini D., “ATF” seismic anisotropy Margheriti L., Wüstefeld A.. Test Site Application to L’Aquila Foreshocks: temporal variations. Piccinini D., Margheriti “L’Aqui Application to the seismic sequence at AQU CAMP and L., Pastori M. la” FAGN stations Table 2 Data set analyzed with the Anisomat+ code.

Figure 6 Map of the ATF test site region; red triangles are seismic stations deployed in 2000; the colors represent normalized delay time. The inset in the lower right corner is the frequency diagram of the fast directions indicating a dominant NW-SE fast in agreement with the SW-NE extension direction of the strain-field in the region. a) Alto Tiberina fault (ATF); b) normal fault; c) Umbria fault system (Gubbio Fault-GuF); d) thrust; e) earthquake M>5.0 : f) wells

WP 2.4 Ground deformation pattern of the Calabro-Peloritani area and the Messina Straits from GPS networks and terrestrial data. Mario Mattia, INGV- CT

1) We analyzed periodical and continuous GPS data collected between 1996.00 and 2008.21 on three geodetic networks installed both on Peloritani Mts., on Aeolian Islands and across the Messina Strait, in order to obtain a detailed spatial resolution of the ongoing crustal deformation (Fig 7). The dilatation strain-rate pattern is dominated by a clear compression of about 0.65 µstrain/yr on a small area located between the Vulcano and Lipari islands. A compression of about 0.1 µstrain/yr can be recognized also between Stromboli and Lipari islands. Across the Nebrodi-Peloritani and the Messina Strait areas the dilatation strain pattern is positive. The areas having maximum values of positive dilatation strain-rate (about 0.15 µstrain/yr) are localized along the two main active fault systems cutting the investigated area: the Messina Strait fault system and the Aeolian- Tindari-Letojanni fault system(see D14).

Figure7 GPS velocity field in the reference frame of Eurasia (Observation time 1996-2008, from Mattia et al 2009)

2) An analysis based on the approach called “elastic block modelling” on the same dataset previously cited, has evidenced that the inter-seismic slip rate of the fault responsible of the 1908 earthquake is of about 3 mm/yr (Fig 8). This result has been achieved through an inversion of the GPS velocity field (Serpelloni et al 2010).

Figure 8 Cross section N124°E (i.e., parallel to the direction of maximum elongation) showing the horizontal velocity gradients (both the profile normal and profile parallel components, where displacements are given with respect to station MPAZ) from optimally inverted fault parameters and slip-rates (green line), where the light dotted lines display fault slip-rate 68% confidence error bounds from the bootstrap analysis. The topographic profile is also shown, together with a cross section of crustal seismicity (including the 1908 earthquake focal mechanism from Boschi et al., 1989) and the modeled geometry and 68% uncertainties from the bootstrap percentile method.

3) Using the Genetic Algorithms (Goldberg, 1989) and the Pattern Search (Lewis and Torczon, 1999) approaches, we carried out a critical examination of the recorded leveling data of Loperfido (1909) showing a significant subsidence (0 ÷ -70 cm) on both side of the Messina Straits, a light uplift in the northern Calabrian side (0 ÷ +3 cm), a largest uplift in the southern Calabrian side (0 ÷ +13 cm) and, finally, no variations in the Sicilian area. We image the 1908 earthquake source using the rectangular dislocation model of Okada (1985) in an elastic, isotropic and homogeneous half- space. We also carried out new sensitivity analysis for the fault parameters obtained fixing the dip angle to a value of 60°. We obtained that the solutions are not well constrained by the available dataset and the network configuration. In particular, the depth and the strike-slip component are totally not resolved. Also the Jackknife re-sampling method provided us large values for the errors of each parameter. Because of these uncertainties, we retain that the available leveling data only are not sufficient to discriminate the source. Any subsequent hypothesis requires the support of robust constraints, obtained for example from seismological and geological data. Moreover, during the Project, we applied the Finite Element method to obtain the displacements compatible with the leveling data (Loperfido, 1909), on the Armo fault and on the summary model of Valensise et al. (2008), in presence of the real topography (Fig. 9; the scale is normalized to the maximum total displacement). In this preliminary work, we chose to use an elastic and isotropic medium. We reconstructed the Armo fault as indicated by field observation (segments AB and CD in Fig. 9). Regarding the summary model (segment EF in Fig. 9), we had a confirmation that the highest displacement was reached on the SW corner of the fault while the NE corner shows smaller displacements Regarding the two segments of the Armo fault, we obtained that the segment AB shows a larger displacement than the segment CD with a maximum in the SW corner.

Figure 9 Total displacement compatible with the leveling data (Loperfido, 1909) and estimated, using FEM approach, on the Armo fault (segments AB and CD) and on the summary model (segment EF) of Valensise et al. [2008]. The scale is normalized to the maximum total displacement. Moreover, on map, the colors indicate the used DEM

Deliverables

# description type authors Restrict. contact person relevance D9 Test of marine Report D’Anna, G., None [email protected] , The seismic and Mangano, G., [email protected] development of deployment Video D’Alessandro, A., [email protected] an Italian OBS D’Anna, R., network is very Passafiume G., Speciale S., important Passarello S. D10 Test of the acoustic Done OBS Lab None [email protected] The acoustic link to get quasi- only in Gibilmanna, link is real time data from the lab Experimental fundamental for OBS stations was Seismology see the development done only in the Laboratory – CNT lab, will be done at report of OBS quasi- sea in October real time 2010 acquisition

D11 Integrated data Data Moretti Available [email protected] In this archive archive of Govoni on the S5 seismic data are continuous Margheriti web site available to the recordings for the Mandiello scientific period October Baccheschi 2007-December Lauciani community 2010 at the Pintore Messina strait test- site D12 Refined Not Moretti None [email protected] earthquakes done, Margheriti locations in the work in Castellano Tyrrhenian and Govoni progress Ionian regions Basili around Messina Bono Strait to define seismogenic structures D13 Code for automatic Script Piccinini, Pastori, Available [email protected] The code speed shear wave and Margheriti, on request up anisotropy splitting manual Bianco,Zaccarelli, evaluations but evaluation Wüstefeld results should be interpreted by an expert

D14 Processing of all maps Mattia M., Palano, Available [email protected] It helps available GPS data M., Bruno, V. and on request understanding for the Messina Cannavò F., the tectonics of strait area, map of Serpelloni, E., the Messina the horizontal Bürgmann R., strain-rate field and Anzidei M., Baldi region computation of the P., Mastrolembo B. inter-seismic strain loading and deep geometry of the 1908 Messina fault D15 Modelling of the maps Marco Aloisi Work in [email protected] It is a work in source responsible progress progress which for the December underlines the 28, 1908 difficulties in earthquake, by using a numeric constraining the approach (i.e. finite 1908 source element)

Problems and difficulties

WP2.1 During the first campaign, within the S5 project, we had some problems with the levelling of seismic sensors Nanometrics Trillium 120 P (INGV Technical Report No. 98: Progetto "Messina 1908 - 2008". Rapporto preliminare della campagna OBS nell'area Eoliana e dello Stretto di Messina; report Phase I project S5); we ordered a new type of seismic sensors and waiting for them we upgraded the mechanical and electronic modules of our OBS. The delivery of new sensors was planned for the August 2009, but for issues associated with the Guralp production, the delivery of the seismic sensors occurred only in November 2009. Because of that delay, the hydrographic vessel “Magnaghi”, available in September thanks to the Italian Navy Hydrographic Institute, was no longer available in November and we had to wait until February 2010 to deploy the OBS / H equipped with new sensors, thanks to a time ship of the research vessel “Urania” of CNR, during the campaign PANSTR10.

The Test of the acoustic link to get quasi-real time data from OBS stations (D10) was done only in the lab, will be done at sea in October 2010

WP2.2 We did not determine new earthquakes locations (deliverable D12) including the temporary stations and so we did not verify if the new network is lowering the detection threshold. This deliverable was not achieved because, the occurrence of the L’Aquila earthquake on April 2009 focused for the last year the attention of the INGV staff involved in this working package (see WP 4.2)and we are only now starting to work on the Messina data..

WP2.3 The application of the code to the earthquakes recorded in the Messina area during the project was not achieved because we did not received the locations from W.P. 2.2.

WP2.4 There were no changes from the original plans.

Publications JCR

2009

Mattia, M., Palano, M., Bruno, V. and Cannavò F., (2009). Crustal motion along the Calabro- Peloritan Arc as imaged by twelve years of measurements on a dense GPS network. Tectonophysics, 476, 528-537, doi: 10.1016/j.tecto.2009.06.006

Pastori M., Piccinini D., Margheriti L., Improta L., Valoroso L., Chiaraluce L. and C. Chiarabba, 2009. Stress aligned cracks in the upper crust of the Val d’Agri region as revealed by Shear Wave Splitting. Geophysical Journal International 1/179(2009) 10.1111/j.1365-246X.2009.04302.x

2010

Serpelloni, E., Bürgmann R., Anzidei M., Baldi P., Mastrolembo B., Boschi E. Strain accumulation across the Messina Straits and kinematics of Sicily and Calabria from GPS data and dislocation modelling. Submitted to EPSL.

Publications non JCR

2008 Margheriti, L. & Messina Team, 2008. Understanding Crust Dynamics and Subduction in Southern Italy, Eos Trans. AGU, 89(25), 225–226.

Margheriti L.,D'Anna G., Selvaggi G., Patane D., Moretti M., Govoni A., Alla ricerca di nuovi dati sulla relazione tra subduzione e cinematica crostale nell’arco Calabro-Peloritano. Capitolo del volume Il terremoto e il maremoto del 28 dicembre 1908 Editors: Bertolaso G., Boschi E., Valensise G.,Guidoboni E..Dec-2008 Publisher:SGA

2009

D’Anna, G., Mangano, G., D’Alessandro, A., D’Anna, R., Passafiume, G., Speciale, S, Amato, A., 2009. Il nuovo OBS/H dell’INGV. Quaderni di Geofisica, 65, ISSN 1590-2595.

D'Anna Giuseppe, Giorgio Mangano, Antonino D'Alessandro, Roberto D'Anna, Giuseppe Passafiume, Stefano Speciale, Santi Passarello Progetto "Messina 1908 - 2008". Rapporto preliminare della campagna OBS nell'area Eoliana e dello Stretto di Messina Rapporto tecnico INGV 2009 n98

Pastori M..Il campo di fratturazione crostale visto dall’anisotropia sismica: presenza di fluidi e loro possibile ruolo nel processo sismogenetico. PhD thesis, Università di Perugia, XXIII ciclo; relazione di II anno.

2010

Moretti M., et al. (2010). “Messina 1908-2008” Progetto di ricerca integrato sull’area Calabro – Peloritana: l’esperimento di sismica passiva”. Quaderno di Geofisica, in press.

Meetings

2008

Pastori M., Piccinini D., Zaccarelli L., Valoroso L., Bianco F., Margheriti L. - Shear Wave Splitting Versus Faults And Stress Field In The Val D'agri (Southern Italy) Analysed With Automatic Procedures. 33rd International Geological Congress (IGC) | Oslo August 6-14th 2008

D’Anna, G., Mangano, G., D’Alessandro, A., D’Anna, R., Passafiume, G., Speciale, S., Selvaggi, G., Margheriti, L., Patanè, D., Luzio, D., Calò, M., 2008. Poster session. Messina 1908-2008 progetto di ricerca integrato sull’area calabro-peloritana: la campagna OBS/H. Extended abstacts: 1908-2008: scienza e società a cento anni dal grande terremoto, 10-12 dicembre 2008, Reggio Calabria.

Moretti M., Govoni A.; Mangano G., D'Anna G., Mandiello A., Margheriti L., et al RU03 | WP 2.1- 2.2: Deployment of an on-land, off-shore seismic network to build up an integrated seismic data archive. Poster Session. 1908-2008: scienza e società a cento anni dal grande terremoto, 10-12 dicembre 2008, Reggio Calabria. Mattia, Mario Valentina Bruno, Mimmo Palano and Flavio Cannavo’ - Crustal motion along the Calabro-Peloritan Arc as imaged by twelve years of measurements on a dense GPS network Extended abstacts:: 1908-2008: scienza e società a cento anni dal grande terremoto, 10-12 dicembre 2008, Reggio Calabria.

Selvaggi Giulio, Lucia Margheriti, Giuseppe D'Anna e Domenico Patanè - "Il Progetto Messina 1908-2008: Nuovi Dati Per Comprendere Relazione Tra Subduzione E Cinematica Crostale Nell'arco Calabro-Peloritano Extended abstacts:: 1908-2008: scienza e società a cento anni dal grande terremoto, 10-12 dicembre 2008, Reggio Calabria.

Cheloni D., N D'Agostino, I Hunstad, G Selvaggi, R Maseroli - Strain Accumulation in the Messina Straits (Southern Italy) From Terrestrial Geodetic Measurements and GPS observations. AGU 2008 Fall Meeting | 15—19 December 2008

D'Agostino N., D Cheloni, F Bernardi, I Hunstad, B Palombo, G Selvaggi - Reassessment of the interseismic and coseismic deformation in the Messina Straits. AGU 2008 Fall Meeting | 15—19 December 2008

Govoni, A., Margheriti, L., D'Anna, R., Selvaggi, G., Patanè, D., Moretti, M. and Zuccarello, L. - Messina 1908-2008: understanding crust dynamics and subduction in Southern Italy AGU 2008 Fall Meeting | 15—19 December 2008

2009

Serpelloni, E., Burgmann, R., Anzidei, M., Baldi, P., & Mastrolembo, B. Strain Accumulation Across the Messina Straits and Kinematics of Sicily and Calabria From GPS Data and Dislocation Modeling, abstract presented at the GNGTS meeting, Trieste, Novembre 2009.

D’Alessandro, A., D’Anna, G., Mangano, G., Panepinto, S., Luzio, D., 2009. Sismicità dell’area Ionica: un’immagine ottenuta da dati OBS. Extended abstacts:, GNGTS, 16-19 novembre 2009, Trieste, vol. 28°, ISBN 88-902101-4-1.

Mandiello A.G., Govoni A., Di Stefano R., Moretti M., Chiaraluce L., Lauciani V., Pintore S., Baccheschi P., Margheriti L., Mazza S. and Selvaggi G. (2009). Complete Uniform and Available Data archive at INGV , First Annual Meeting, October 19-21, 2009.

Serpelloni, E., Burgmann, R.; M. Anzidei; P. Baldi; B. Mastrolembo Strain Accumulation Across the Messina Straits and Kinematics of Sicily and Calabria From GPS Data and Dislocation Modeling, EOS Trans. Abstract G22A-04 presented at the AGU 2009, Fall Meet. Suppl.;

Mastrolembo Ventura, B., Serpelloni, E., Burgmann, R., Anzidei, M., Baldi, P. & Cavaliere, A. Active strain-rates across the Messina Straits and kinematics of Sicily and Calabria from GPS data, Geophysical Research Abstracts, Vol. 11, EGU2009-9870-1, 2009, abstract presented at the EGU General Assembly 2009;

Monaco C., Aloisi M., Ferranti L. and M. Mattia (2009). Possible fault models for the 1908 earthquake (Messina Straits) based on the inversion of levelling data and morphotectonic features. FIST 2009. 2010

D'Anna, G., Mangano, G., D'Alessandro, A., 2010. The OBS experience at INGV. NERIES- ESONET OBS-Marine Seismology Workshop, 11-12 Feb. 2010, Paris, France.

D'Alessandro, A., Luzio, D., D’Anna, G., Mangano, G., Panepinto, S., 2010. Single station location of small-magnitude seismic events recorded by OBS in the Ionian Sea. Geophysical Research Abstracts, EGU General Assembly, Vienna, Austria, 02-07 May 2010, vol. 12°, EGU2010-8840.

Mastrolembo, B., Serpelloni, E., Burgmann, R., Anzidei, M., Baldi P., Strain accumulation across the Messina Straits and Crati Valley and kinematics of Sicily and Calabria from GPS data and dislocation modeling, EGU2010-12674, abstract presented at the EGU General Assembly 2010;

D'Anna Giuseppe e Giorgio Mangano | Sea Bottom Seismograph installation and data transmission testing through acoustic. Meeting S5 march 24th 2010.

Moretti Milena Integrated on-land and off-shore seismic data bank and refined earthquake location Meeting S5 march 24th 2010.

Piccinini Davide Seismic anisotropy analysis aimed at defining the present crustal deformation regime Meeting S5 march 24th 2010

Mattia Mario and Palano Mimmo Strain field of Calabria and Peloritano regions from GPS data acquisition and modeling Meeting S5 march 24th 2010. Section 2: Report on the S5 project Task2 by UR4, G. Neri The second phase activities of the UR-Messina consisted in the conclusion of focal mechanism computation, the integration of the computed FMs in the available database and the seismogenic stress fields estimation in the Messina Straits area. The UR–Messina, in collaboration with the Earth & Atmospheric Sciences Department of Saint Louis University, has applied in the Straits area the “Cut And Paste” (CAP) method for moment tensor estimation (Zhao and Helmberger, 1994, Zhu and Helmberger, 1996). To obtain the Green’s functions we performed the frequency-wavenumber (f-k) integration as described in Zhu and Rivera (2002) for a distance range from 5 to 500km and a focal depth range from 2 to 60km (horizontal and vertical grid spacing is of 5km and 2km, respectively) . One of the advantages of the CAP method is that each waveform is broken up into the Pnl and surface wave segments that are fit using a grid search to obtain the best moment magnitude, source depth and focal mechanism. CAP has been shown to be very stable also for earthquakes of magnitude as small as 2.5÷3. For this reason it is very useful in the Messina Straits area, characterised in the last decades by microearthquake activity. So we focus on earthquakes of magnitude greater than 3 occurred during the period 2004-2008 and we apply the CAP method by integrating the data of the National Seismic network with the broad band recordings coming from temporary stations of the Messina 1908-2008 Project. We relocated these events using the BAYLOC non-linear probabilistic location method by Presti et al. (2004, 2008) and the 3-D seismic velocity model proposed for the study area by Barberi et al. (2004). In order to have an additional check of the CAP focal mechanisms for the study area we performed several tests. For some of the earthquakes investigated, we tried different station distributions, such as using only the nearest, the farthest stations or combinations of both. We also changed the azimuthal station distribution and the hypocentral parameters of the event. Figure 1 shows the results of this sensitivity testing for one of the earthquakes. The focal mechanism is robustly determined. In fact, we found that just a few stations provide enough information to properly constrain the focal mechanism of the earthquake. Furthermore, we note that azimuthal gaps as large as 180° in station distributions do not significantly change the solution. Finally, we may observe that the solution is stable in the error range of the focal depth estimated by CAP. For some events we also applied the waveform inversion technique of Herrmann (2008) to get the moment tensor solution as a check on our computations. His approach models the entire ground velocity waveform and uses a different technique for computing Green's functions. The focal mechanisms obtained using the two different methodologies are in good agreement. Figure 1 displays also the published INGV-RCMT solution of the same event (Ekstrom et al.,1998; Pondrelli et al., 2006).

Figure 1 Examples of tests and comparisons made to check the quality of the CAP solutions obtained in the present project. The panel A shows the location of the event ID 20060227a and of the stations used in the tests displayed here. The beach balls in the panel B represent the solution obtained using some nearby stations (a), some farther stations (b), a combination of them with an azimuthal gap of almost 180 degrees (c), forcing the epicenter to lie 5 km south of the true location (d) and using only the surface wave segments (e). The solutions obtained at different depth levels around the CAP focal depth of the event are displayed in the panel C with the corresponding values of the predicted-observed waveform misfit. Finally the panel D shows, for comparison, our CAP solution, the focal mechanism we estimated by the method of Herrmann (2008) and the regional CMT solution released by INGV (http://www.bo.ingv.it/RCMT/searchRCMT.html).

We have also checked the stability of the mechanisms varying the earth structure parameters within ranges defined according to the most recent tomographic inversions and velocity models available for the study area (see e.g. Barberi et al., 2004; Neri et al., 2010). For this test we started from the tomographic models of Barberi et al. (2004) and Neri et al. (2010) and computed in both structures the P-wave theoretical travel-times corresponding to the source-station pairs used for the CAP inversion. Then, from the time-distance plots obtained for the respective structures we derived the 1D velocity models. The differences among these models represent wave propagation across the laterally heterogeneous crust of the study area (Neri et al., 2002; Finetti, 2005; Pontevivo and Panza, 2006). We found high stability of CAP solutions when the model changes. The CAP method, successfully applied to study earthquakes with magnitude lower than 3 in other regions (Zhu et al., 2006), is able to furnish good quality solutions in the Messina Straits area in a magnitude range (3-4) which is not properly represented in the RCMT (Regional Centroid Moment Tensor) catalog (Pondrelli et al., 2006) and where the solutions estimated from P-onset polarities are often poorly constrained. Figure 2 shows that normal faulting is the main style of seismic deformation in the Messina Straits area. Using the Zoback’s WSM terminology (Zoback, 1992; http://dc-app3-14.gfz-potsdam.de/) we count 10 normal faulting mechanisms (NF), 7 normal-strike (NS), 5 strike-slip (SS) and 1 undefined (U). We may note from the map that the regime of faulting significantly changes from north to south: normal faulting prevails clearly in the north while it appears mixed to strike-slip in the south. According to WSM terminology we count 9 NF earthquakes, 3 NS and 2 SS in the northern sector A of the study area and 4 NS, 3 SS, 1 NF and 1 undefined in the southern sector B. We have also checked that the sub-volumes A and B effectively allow for the best separation between the normal faulting earthquakes and the others.

Figure 2 Focal mechanisms estimated in the present study by the CAP waveform inversion method. The polar plots of P and T axes relative to sub-areas A and B are also shown. Black and white dots in the polar plots correspond to P and T axes, respectively.

The data outline a clear north-to-south variation of the seismic deformation style marked by the dashed line separating the sub-volumes A and B. The polar plots of P- and T-axes in A and B show the different styles of deformation, with the P-axes more clustered near the center in the case of plot A. This behavior is also supported by the stress inversion of the focal mechanisms of Figure 2 performed by using the Gephart and Forsyth (1984) algorithm. We found a sub-vertical attitude of σ1 and an approximately WNW-ESE orientation of σ3 in the whole study area. The misfit of 6.2° indicates a moderate stress heterogeneity (Wyss et al., 1992; Gillard et al., 1996; Neri et al., 2004) as already highlighted by the focal mechanisms distribution. Therefore we separately inverted for the sub-volumes A and B previously identified. Stress field of sub-volume A is the same of the entire area and shows a lower misfit value (4.4°) and smaller uncertainty areas. The stress axes orientation of sub-volume B, even if poorly constrained because of the few FMs, still indicates a prevalently extensive regime but with a different orientation of extension (c.a. E-W). Similar results have been obtained including in the datasets fault plane solutions coming from the RCMT catalog. In conclusion, the results obtained by our RU in the framework of S5 Project may be interpreted by considering that the Messina Straits area is transitional between the extensional domain of south- western Calabria and the compressive domain of Western-Central Sicily. The co-existence of normal faulting and strike-slip mechanisms that we have found provides new data in support of the above interpretation of the local geodynamics. Normal faulting (with NW-SE preferential direction of extension) is the response to the residual rollback of the subducting slab and south-eastward trench retreat still occurring at very low speed in southern Calabria. In fact, seismogenic normal faulting characterized by this study is more pronounced in the northern portion of the area, e.g. in the sub-area A more favourably oriented with respect to trench retreat representing the source of extension. The subducting trench retreat combined with the continuing plate convergence due to northwestward Nubia motion generates a dextral transfer zone across northeastern Sicily and the Messina Straits and, therefore, explains the strike-slip mechanisms and the different orientation of σ3 found in the southern part B of our study area. These results bring new data on the seismogenic mechanisms in the study area. The already existing information coming from the application of waveform inversion methods (CMT, RCMT and TDMT) is limited to 6 data only relative to earthquakes of magnitude greater than 4. The solutions estimated by inversion of P-onset polarities (Frepoli and Amato, 2000; Gasparini and Vannucci, 2004; Neri et al., 2004) are affected by uncertainties larger than 15-20° due to poor network geometry caused by offshore location of many events and the lack of OBSs in the study. The traditional focal mechanism solutions have focal parameter errors small enough to allow detection of strong stress variations between the Calabrian Arc and Western-Central Sicily major domains, but the errors are too large for detection of more subtle stress changes in the transitional area between the main domains. The new data obtained in the frame of this Project can lead us to make some progress in the knowledge of tectonic stress accumulation mechanisms and consequent processes of seismogenic faulting in the area of our interest. In the framework of the same Project, the RU4 provided moment tensor solutions for the L’Aquila sequence by using the foreshocks and aftershocks of the Mw 6.3, 6 April 2009 L’Aquila earthquake. The moment tensor solutions computation was performed by using the CAP method – briefly described above - originally proposed by Zhao and Helmerger (1994) and later modified by Zhu and Helmerger (1996). We started by compiling a list of all earthquakes in the study area from the INGV seismic catalogue (http://iside.rm.ingv.it) for the time period from April, 1 st 2009 to end of March 2010 with focal depths less than 25 km and magnitudes Ml larger than 2.8. The dataset was restricted to the earthquakes recorded at a minimum of 4 three-component seismic stations equipped with broad-band sensors and located within about 200km from the epicenter. Each waveform was examined to eliminate recordings with spurious transients or low signal-to-noise ratios and corrected for the instrument response to yield to ground velocity. Finally the peaking of P-arrivals was reviewed and the horizontal recordings were rotated to radial and transverse components. We were able to compute moment tensor solutions for small and moderate earthquakes not often included into the national moment tensor catalogues due to the lower magnitude threshold investigated. The solutions exhibit normal faulting and almost all tension axes are in the E to ENE directions (Figure 3).

Figure 3 Map of the focal solutions computed by using the CAP method for about 300 events of the L’Aquila 2009 sequence.

Results obtained in the framework of this Project are in good agreement with the 26 solutions proposed by Pondrelli et al. (2010) in the magnitude range between 3.9 and 6.3 by using RCMT technique. Our results, including small and moderate earthquake, can be useful for obtaining remarkable progresses in the knowledge of tectonic stress accumulation mechanisms and the consequent refining of seismogenic faulting in the study area.

Results obtained in the project framework The area of the Messina Straits studied in the framework of the project is approximately bounded by latitudes 37.8N to 38.5N and longitudes 15E to 16E and is monitored by National Seismic Network which is managed by the Istituto Nazionale di Geofisica e Vulcanologia (INGV). We selected from the INGV seismic catalogue (www.ingv.it) all earthquakes recorded in this area from October 2004 to October 2008, in the magnitude range of Ml 3.0-4.1 The final data set we used in this study consisted of waveforms from 23 earthquakes; we relocated the events by using the BAYLOC method by Presti et al. (2004, 2007) and used the 3-D velocity model proposed for this area by Barberi et al. (2004). We computed the moment tensor solutions using the “cut and paste” method based on broadband waveform inversion (Zhu and Helmberger, 1996, and Zhu et al., 2006). The obtained focal solutions have been integrated with the data available in the official databases and in the literature. The already existing information coming from application of waveform inversion methods (CMT, RCMT and TDMT) is limited to 6 data only relative to earthquakes of magnitude greater than 4. The solutions estimated by inversion of P-onset polarities (Frepoli and Amato, 2000; Gasparini and Vannucci, 2004; Neri et al., 2004) reveal the “gross feature” of prevailing normal faulting but do not indicate any other significant feature. New data show that the regime of faulting significantly changes from north to south: normal faulting prevails clearly in the north while it appears mixed to strike-slip in the south. Normal faulting (with NW-SE preferential direction of extension) is the response to the residual rollback of the subducting slab and south-eastward trench retreat still occurring at very low speed in southern Calabria. In fact, seismogenic normal faulting characterized by this study is more pronounced in the northern portion of the area, e.g. in the sub-area A more favourably oriented with respect to trench retreat representing the source of extension. The subducting trench retreat combined with the continuing plate convergence due to northwestward Nubia motion generates a dextral transfer zone across northeastern Sicily and the Messina Straits and, therefore, explains the strike-slip mechanisms and the different orientation of σ3 found in the southern part B of our study area. We also provided moment tensor solutions for the L’Aquila sequence by using the foreshocks and aftershocks of the Mw 6.3, 6 April 2009 L’Aquila earthquake and the CAP waveform inversion method. We were able to compute moment tensor solutions for small and moderate earthquakes not often included into the national moment tensor catalogues due to the lower magnitude threshold investigated. The solutions exhibit normal faulting and almost all tension axes are in the E to ENE directions.

Deliverables

# descript type authors restrict contact relevance ion ions person D16 focal Digit D'Amico, S., none sebdamico@g The well-constrained focal mechani al Orecchio, B., mail.com; mechanisms of low/moderate sm table Presti, D., dpresti@unim earthquakes have been useful to estimate Zhu, L., e.it detect subtle stress changes in the d in the Herrmann, R. Messina Straits area related to the Messina B., Neri, G. transition between the extensional Staits domain of south-western Calabria area and the compressive domain of Western-Central Sicily.

D17 main Digit D'Amico, S., none orecchio@uni The new moment tensor data led paramet al Orecchio, B., me.it; us to make some progress in the ers of table Presti, D., Neri, dpresti@unim knowledge of tectonic stress the G. e.it accumulation mechanisms and stress consequent processes of fields seismogenic faulting in the area of interest of the Project.

DAQ 5 focal Digit D'Amico, S., Availa sebdamico@g Moment tensor solutions for mechani al Orecchio, B., ble on mail.com; small and moderate earthquakes sm table Presti, D., Zhu, request orecchio@uni not often included into the estimate L., Herrmann, me.it national moment tensor d in the R. B., Neri, G. catalogues. L’Aquil a area

Table 1

High quality focal mechanism estimated during the Project. As explained in the text, the CAP method has been used for computation of the focal depth H; the fault parameters, strike, dip and rake; and the magnitude Mw. Focal depth and fault parameter uncertainties have been estimated with the method described by Tan et al. (2006) and herein referred papers

ERR ERR ERR Event ID O.T. Lon (°E) Lat (°N) H (km) ML Mw Strike(°) Dip(°) Rake(°) (Strike) (Dip) (Rake) 20041011 7.31.41 15.48 37.88 6.6 3.5 3.6 89 90 -45 1 1 1 20041022 21.10.13 15.32 38.08 10.7 3.5 3.4 78 61 -37 0 1 2 20050419 22.36.23 15.66 38.14 7.1 3.2 3.1 220 42 -10 1 2 2 20050423 19.10.48 15.82 38.43 13.6 3.0 2.8 120 50 -64 1 1 2 20050814 22.02.27 15.12 37.80 6.7 3.0 3.1 82 50 -18 1 1 1 20060227a 4.34.01 15.17 38.10 10.1 4.1 4.1 62 50 -71 0 1 2 20060227b 9.11.59 15.18 38.14 10.5 3.5 3.1 39 48 -90 2 1 2 20060227c 14.16.06 15.18 38.14 9.1 3.3 3.1 76 48 -58 1 1 3 20060702 17.52.00 15.10 38.13 10 3.0 2.6 70 59 -49 1 2 3 20060718 7.42.40 15.17 38.12 9.1 3.3 3.1 90 41 -49 1 1 2 20061006 21.16.23 15.57 38.10 9.6 3.2 3.2 18 52 -90 1 1 2 20061104 5.59.22 15.01 38.03 10.6 3.1 3 59 49 -37 1 2 4 20070617 12.11.58 15.79 38.37 10 3.3 2.9 262 38 -43 1 2 1 20070818a 14.04.07 15.13 38.23 9.4 4.0 3.9 44 50 -23 1 1 2 20070818b 14.21.11 15.12 38.19 10 3.2 3.4 26 69 18 2 3 5 20080209 7.46.36 15.56 37.84 6.9 3.1 3 40 90 -10 1 1 2 20080413 13.06.57 15.70 38.25 14.3 3.3 2.8 6 51 -30 2 1 2 20080501 21.05.49 15.07 37.80 2 3.4 3.4 96 76 2 1 1 3 20080513 21.28.30 15.06 37.80 12 3.3 3.5 76 46 -20 1 1 2 20080705 17.04.36 15.87 38.20 2 3.0 2.6 311 59 2 1 1 4 20080901 14.45.40 15.06 37.97 8.1 3.1 3.1 70 31 -80 0 1 3 20080902 9.16.45 15.06 37.99 10.3 3.4 3.3 279 64 -44 1 1 2 20081027 10.55.55 15.13 38.11 2 4.0 3.5 50 28 -71 0 1 2

Table 2

Main parameters of the stress fields computed by using the Gephart and Forsyth (1984) algorithm.

Sector N. of events σ1-az σ1-pl σ2-az σ2-pl σ3-az σ3-pl Average misfit F

study area 25 211° 68° 34° 21° 304° 1° 6.2°

A 14 211° 68° 34° 21° 304° 1° 4.4°

B 9 341° 65° 187° 22° 93° 10° 3.1°

Problems and difficulties

No problem did rise during the second year of activities

Publications D'Amico, S., Orecchio, B., Presti, D., Gervasi, A., Zhu, L., Guerra, I., Herrmann, R. B., Neri, G., 2010. Testing the stability of focal mechanism solutions for small and moderate earthquakes in the calabrian-peloritan arc region. Submitted to Bollettino di Geofisica Teorica ed Applicata. D'Amico, S., Orecchio, B., Presti, D., Zhu, L., Herrmann, R. B., Neri, G., 2010. Broadband waveform inversion of moderate earthquakes in the Messina Straits, southern Italy. Physics of the Earth and Planetary Interiors, 179, 3-4, 97-106. D’Amico, S., Orecchio, B., Presti, D., Gervasi, A., Guerra, I., Neri, G., Zhu, L., Herrmann, R., 2010. Broadband Source Mechanism Modeling of Recent Earthquakes in Calabria, Southern Italy. Seismological Society of America, Annual Meeting, Portland, Oregon, 21-23 April. Orecchio, B., D'Amico, S., Gervasi, A., Guerra, I., Presti, D., Zhu, L., Herrmann, R. B., Neri, G., 2009. Moment tensor solutions of recent earthquakes in the Calabrian region (south Italy). Abstract presented at AGU Fall Meeting, S. Francisco, 14-18 Dicembre. D'Amico, S., Orecchio, B., Presti, D., Zhu, L., Herrmann, R. B., Neri, G., 2009. Moment tensor solutions of recent earthquakes in the Messina Straits area, southern Italy. Seismological Society of America, Annual Meeting Monterey, CA, (USA), 8-11 April. Seism. Res. Lett., 80 (2), 321. D'Amico, S., Orecchio, B., Presti, D., Gervasi, A., Guerra, I., Zhu, L., Herrmann, R. B., Neri, G., 2009. Moment tensor solutions of low-magnitude recent earthquakes in the Calabrian- Peloritan Arc region. Abstract presented at XXVIII Convegno Nazionale del G.N.G.T.S., Trieste, 16-19 Novembre. D'Amico, S., Orecchio, B., Presti, D., Neri, G., Zhu, L., Herrmann, R. B., Source parameters of small and moderate events in the area of the Mw 6.3 L’Aquila earthquake (central Italy), in preparation.

Section 2: Report on the S5 project by UR5 Antonio Avallone Since 2003, INGV deployed a continuous GPS network (RING, http://ring.gm.ingv.it ) in order to study the complex pattern of deformation in the Central Mediterranean, at the plate boundary between Africa and Eurasia. Most of the CGPS sites, acquiring at 1Hz and 30s sampling rate, are integrated either with broad band and very broad band seismometers or accelerometers for an improved definition of the seismically active regions. Most of the sites are connected to the acquisition centre (located in Rome and duplicated in Grottaminarda) through a satellite system (VSAT), while the remaining sites transmit data by Internet and classical phone connections. Both the satellite and the Internet data transmission allow the real-time epoch by epoch data acquisition at the acquisition centres. In the figure 1-left we show the location of all the CGPS sites which are acquiring and transmitting data in real-time. This network represents the high-rate GPS reference network outside the investigated area, such as the Irpinia region. In the figure 1-right, we show the locations of all the RING sites present in the Irpinia area. All the sites present in this figure transmit data in real-time: green triangles represent sites transmitting data at 1Hz, while red triangles correspond to sites transmitting data with a rate of 1 epoch every 30s.

Figure 1: (left) Present-day RING Real-time network (1Hz or 30s transmission rate); (right) present-day real-time (1Hz, green, and 30s, red) network in Irpinia area.

Most of the sites in Irpinia transmit data either by satellite telemetry (every 30s) or by Internet connections (every 1s). The Internet connection is assured by using the GPRS/UMTS technology (Falco, 2008). We choose an alternative and redundant transmission type to assure the acquisition of the data, which represent a fundamental aspect in case of emergency. The High-rate data acquisition at the sites in Irpinia represents one of the topics of the project, because the quick estimation of the potential co-seismic dislocations at RING sites after an earthquake strongly depend on the latency of the acquired data. The 1Hz data are stored in Rome and Grottaminarda with a ringbuffer strategy spanning a period of 1 week, thus assuring a sufficient amount of data to retrieve co-seismic and immediately successive post-seismic signals. In case of event, the ringbuffer is turned off and the data are stored in the hard disk. The other main aim of the workpackage 3.4 in the 1 st year consisted in learning how to analysis the acquired high rate GPS data. Traditionally, the active tectonics studies require a GPS data processing strategy which allows to obtain a daily solution with data sampling rate at 30s. However, in this project, the need to obtain quick determinations of the co-seismic displacements at the CGPS sites after an earthquake, constrain us to process GPS data with a completely different strategy. The data should be analyzed epoch by epoch. We used the Gipsy/Oasis II software, a non-commercial geodetic-quality software developed at JPL (Zumberge et al., 1997). For the epoch by epoch analysis we used the “ gd2p ” Gipsy module to obtain a kinematic solution for each site. The kinematic solution allows us to carry out, for each epoch, the position of each site with respect to its nominal a-priori precise position. The analysis uses data for all the satellites located above an elevation angle of 15° with respect to the horizon. Holding the precise high-rate JPL orbits and clocks fixed, we use a procedure to estimate station positions and clocks and troposphere delay. To verify the procedure, we analyzed the data of the CGPS sites that recorded the 2004 Sumatra earthquake and that are described in the work of Blewitt et al. (2006). After applying the sidereal filtering, the results obtained for the stations SAMP and NTUS are perfectly comparable to the ones obtained by Blewitt et al. (2006) (Figure 2).

Figure 2: (top) Co-seismic displacements detected at NTUS and SAMP sites in occasion of the 2004 Sumatra earthquake by Blewitt et al. (2006). (bottom) Co-seismic displacements detected at NTUS and SAMP sites obtained with this study.

The occurrence of Mw 6.3 L’Aquila earthquake represented an unique ensemble of peculiarities: for the first time, a moderate magnitude earthquake has been recorded by 10 Hz sampling GPS data at two sites located just on the activated fault (“near source”) and for the first time, we obtained 10 Hz GPS results by using a single station (PPP) approach (Figure 3), which was crucial for the L’Aquila earthquake, because no GPS receivers were sampling with the same rate outside the epicentral area. As expected, the 10Hz solutions allow to detect a more detailed dynamic displacement than the 1Hz solution. In ROIO, the deformation starts 2.3s after the nucleation, as it is closer to the earthquake nucleation point than CADO, for which the deformation starts later (3.7s). For both the sites, the vertical components clearly show a subsidence occurred in three steps reaching values temporarily bigger than the definitive co-seismic displacement. ROIO and CADO experienced maximum subsidence values of 13.9 cm and 17.7 cm, respectively.

Figure 3: 10Hz-sampled (continuous line) and 1Hz-sampled (dashed lines) co-seismic displacements obtained at ROIO (left) and CADO (right) sites in occasion of the 2009 L’Aquila earthquake. Red, green and blue colors represent the North, East and Vertical components, respectively. Vertical thin line indicates the L’Aquila earthquake time occurrence (01:32:40.78)

On the other hand, the horizontal components show different aspects for the two sites. The first seismic horizontal pulses of ROIO are both positive (towards NE), whereas CADO shows a mainly north-northwestward first horizontal pulse. Furthermore, on the horizontal components, about 5s after the beginning of the dynamic deformation, both the 10Hz GPS solutions show a movement apparently regular in frequency (around 1Hz) that starts with a high amplitude pulse, followed by a displacement that rapidly decreases in amplitude and reaches the noise level after 6.5-6.8s. This later displacement seems to occur after having already reached the definitive co-seismic horizontal offset. If this high-amplitude signal is related to a sort of site effect (i.e. topographic effect) or to the seismic wave propagation or to some source effects (i.e. stop phase) is still unclear and it warrants to be investigated in further more detailed studies in the next future. The L’Aquila seismic sequence gave us the opportunity to investigate also the minimum magnitude threshold that can be detected by this technique.

For that, we analyzed the high-rate GPS data also for the days of the main aftershocks occurred within the first month and only the main aftershock (Mw 5.6), occurred on April,7 th 2009, has been successfully detected (Figure 4). The figure 4 shows that no co-seismic offset is observed for this aftershock and only the high-amplitude signal (present also in the mainshock GPS solution) appears. This study confirms the GPS capability to accurately detect also the first seismic arrivals for moderate magnitude earthquake (Mw 5.6-6.3), if GPS sites are opportunely located and set up with very high-rate sampling. Thus, dense continuous GPS networks with very high-rate sampling intervals will be very helpful in detecting significant variations in the seismic waves propagation, that could be related to rupture dynamics or otherwise hidden geologic heterogeneities. Furthermore, dense real-time transmitting continuous GPS networks (as the RING network, http://ring.gm.ingv.it ) can be fully exploited to detect quick mean co-seismic displacements. Of course, this purpose can be achieved also acquiring data with more “traditional” sampling rates. As mentioned above, the GPS data analysis can be performed by using additional information, such as satellite orbits and clocks. The final (and more precise) orbits are available with a ~12-18 days latency. However, recent developments in the GPS orbit determination provided reliable results also for rapidly estimated orbits, which are available with a 17-41 hours latency (~1 day). Thus, we analyzed the GPS data acquired during the L’Aquila earthquake to obtain 5-min solutions by using rapid orbits and we compared the obtained solutions with those obtained by using final orbits. For this comparison we used both JPL (Jet Propulsion Laboratory) and IGS (International GPS Service) products (Figure 5).

Figure 5: Comparison, for each component, between the 5-min solutions carried out by using IGS and JPL final and rapid orbits.

The figure 5 shows that co-seismic displacements resulted during the L’Aquila earthquake from the solution with rapid orbits is almost coincident with the solution with final orbits. Thus, the comparison between final and rapid orbits demonstrates that we are able to obtain a quick co- seismic mean displacement detection within about 1 day from the earthquake, without significant loss of accuracy.

Results obtained in the project framework High-rate GPS acquisition : All the RING sites located in Irpinia area transmitting data in real- or quasi real-time by using satellite telemetry, GPRS/UMTS or Wifi technology. This aspect has a very high impact for further studies on quasi real-time GPS seismology. High-rate GPS processing : A kinematic solution in post-processing is performed to obtain the variation of the position of each GPS site with respect to its nominal a-priori precise position by using Gipsy/OASIS II software. The kinematic analysis has been applied to the L’Aquila earthquake. The L’Aquila earthquake results provided for the first time very high-rate GPS solutions with a single station analysis. High-rate GPS procedure for alert systems : The comparison between the solutions obtained by using both final and rapid orbits and clocks allows us to confirm the feasibility of creating a procedure to obtain a mean co-seismic displacement with a 1day latency. This aspect has a potentially high scientific relevance, because a customized procedure could allow to retrieve first co-seismic displacements of the permanent GPS sites to constrain the activated fault (1day) before any discrete GPS field survey results (3-4 days). Analysis of earthquake detection thresholds : We analyzed the high-rate GPS data acquired during strongest shocks (Mw > 4) occurred after the L’Aquila mainshock and we could detect only the dynamic displacements related to main aftershock (Mw 5.6), occurred on April, 7 th , 2009 at a depth of about 15 km. This result has a very high relevance because for the first time, such a moderate magnitude earthquake has been observed by GPS.

Deliverables # description type authors restrictions contact relevance person D24 Acquisition, Station list, D’Ambrosio data storage Avallone A. High storage, analysis storage internet C., Falco L., temporarily and addresses, Avallone A., with restricted modelling of description of access high-rate GPS the analysis data in the script Irpinia test site

Problems and difficulties A 3-months delay in the planned work has been represented by the beginning of the fellowship founded by this project. The fellowship started on August, 1 st , 2008, while the project started on May, 1 st , 2008. Furthermore, because of the occurrence of the 2009 L’Aquila earthquake, most of the people involved in this project were devoted to perform discrete GPS measurements in the epicentral area to obtain a co-seismic displacement and a first model of the activated fault. Moreover, some people involved in this project collaborated to create three new permanent GPS stations to study the post-seismic effect related to the earthquake.

Publications Avallone A, Marzario M., D’Anastasio E., D’Agostino N, Cecere G., D’Ambrosio C., Falco L., Abruzzese L., Cardinale V., De Luca G., Memmolo A., Minichiello F. and Zarilli L., 2009. RU5: High Frequency GPS as a potential contribution for monitoring a seismogenic structure, Poster at 1 st annual DPC meeting, Rome (Italy), October 19-21 2009. Avallone, A., Marzario, M., Cirella, A., Piatanesi, A., Rovelli, A., Di Alessandro, C., D'Anastasio, E., D'Agostino, N., 2009. Using high-rate (10Hz) GPS data for studying the L’Aquila earthquake, Abstract presented at the GNGTS Meeting, Trieste (Italy), November 18 2009. Avallone, A., Marzario, M., Cirella, A., Piatanesi, A., Rovelli, A., Di Alessandro, C., D'Anastasio, E., D'Agostino, N., 2009. 10Hz GPS Seismology for moderate magnitude earthquakes: the case of the Mw 6.3 L'Aquila event, Abstract presented at the AGU Fall Meeting, Abstract U13C-06, San Francisco (CA), December 14-18 2009.

Report on the S5 project by UR6 Prof. Aldo Zollo

Results obtained in the project framework In the framework of the S5 project, this research unit has carried out research activities in TASK 3 (The Irpinia Fault System monitoring site) WP3.1, WP3.2 and WP3.3 and TASK 4 (L’Aquila test site in WP4.3). This final report summarizes the obtained scientific achievements and results in each workpackage pointing out their impact, relevance for Civil Protection and scientific community and degree of innovation.

Task 3 - The Irpinia Fault System monitoring site (Task Responsible: Aldo Zollo) The work objectives pursued by our RU within Task 3 have been : - to explore the feasibility of using continuously recorded seismic noise to extract information about the velocity structure beneath the recording network and use the spectral analysis of noise records to monitor the station state of health and functioning - to develop automatic and semi-automatic procedures for the refined analysis of arrival-timea and waveforms of micro-earthquakes with the aim to get accurate earthquake location and source parameter, in addition to attenuation properties of the medium - to infer 3D smooth/rugged models of the shallow crust and fault zones in the region southern Apennines WorkPackage 3.1: Seismic noise (WP responsible: Gaetano Festa) The main objective of this WP was the use of cross-correlated seismic ambient noise for the extraction of the propagation features associated to surface waves, which dominate the Green functions when both source and receivers are located at the Earth free-surface. We used broad-band records at five stations of the ISNet collected along two years (from June 2008 to May 2010), and processed them in order to keep only phase information and cancel out any artifact related to anomalous amplitudes (earthquakes, spikes, atmospheric effects, etc.). For that, data have been equalized in both frequency and time domains by whitening and one-bit normalizations. Finally records from couples of stations have been cross-correlated and stacked to build up a database of Green’s functions from ambient noise. It is worth to note that, within this procedure, we also investigated the properties of the ambient noise by Power Spectral Density (PSD) analysis, which discerns in frequency domain stable regimes from bands in which the ambient noise rapidly changes. PSD also revealed a valid instrument to (semi)automatically detect the correct operating of a seismic station and it is now routinely used in ISNet for this aim. To check the quality of the Green function its upper frequency value at which it is stable, we applied several techniques for data-preprocessing, by switching on and off the whitening, by recursive filtering the data and by selecting the cross-correlated records according to several specific definitions of the Signal-to-noise ratio. We realized that no improvement larger than few percent is gained in such ad-hoc procedures, indicating that ambient noise features are mostly stable with time and automatic procedures are able to detect them. From inspection of cross-correlated traces and seismic sections, surface waves have been extracted from Green functions and processed via a time-frequency multiple-filter analysis (software sacmft96, Herrmann and Ammon, 2002) to investigate the dispersive response of the structure for shallow propagating waves. Time-frequency paths for couple of stations have been manually picked following the maximum energy distribution along the spectrograms. Then, group velocity dispersion curves are obtained by dividing the distance between the two stations by the picked time at each frequency. We observe that most of the energy is concentrated in the frequency band 0.15- 0.5 Hz, with a minimum localized at 0.2-0.3 Hz, indicating the presence of mostly 1D layer Figure 1 Refined earthquake locations and selected focal mechanisms. The ISNet stations are also shown underlying the investigating area. Some energy is observed also at lower frequencies (between 0.04 and 0.05 Hz), with low group velocities, which well propagates in the area of interest, but the origin of which has still to be investigated. As a first approach, we inverted the dispersion curves to obtained a 1D velocity model for the S waves in the Irpinia Region using the surface wave inversion program Surf96 (Herrmann and Ammon, 2002). We fixed the ratio Vp/Vs to 1.8, which is the value obtained by location of earthquakes from P and S first arrivals. We found that a two- layer model well fits the dispersion curves, with the first interface located at 2.1 Km of depth, across which Vs jumps from 2.1 Km/s to 3.3 Km/s.

WorkPackage 3.2: Refined estimates of micro-earthquake source parameters (WP responsible: Claudio Satriano)

The objective of this work package is to achieve high-resolution images of the Irpinia active fault system through the accurate determination of source parameters of micro-earthquakes in the magnitude range 1

detected events.The data set is further extended and integrated by the inclusion of the closest stations of the Italian Seismic Network, managed by INGV. The current database comprises more than 900 events (from Aug 2005 to April 2010) inside the network and in the surrounding area with 0.5 < Mw < 4. An accurate manual re-picking has been performed on the whole data set, for a total number of about 57000 3-component recordings. The first step of our analysis was to define an appropriate velocity model for earthquake location, and focal mechanism determination. For this purpose an accurate revision of the manual picking has been performed through the analysis of data outliers on: (1) the modified Wadati diagram (Chatelain, 1978), which also provides a preliminary estimate of Vp/Vs (1.87), and (2) the histograms of station residuals, obtained after a preliminary location. We further selected from the original data set a subset of 230 well-constrained earthquakes, characterized by a maximum gap of 200°, with a minimum of 5 P-wave arrival time readings, and we used this refined data set to determine a minimum 1D model for the region, through the Velest code (Kissling et al., 1994). Earthquake locations in this new model have been obtained through a joint hypocentral determination, using a non-linear, probabilistic location software (NonLinLoc, Lomax et al. 2000). Then, the whole catalog has been relocated using the HypoDD code (Waldhauser and Ellsworth, 2000).

Figure 2 Source parameter scaling laws from the Irpinia We estimated the earthquake focal fault system as inferred from the inversion of microearthquake displacement spectra. Top figure. Corner mechanisms, from about 2500 P-wave first- frequency vs Seismic moment. Closed and open circles motion polarities, using the FPFIT algorithm represent measurements from the S- and P-wave spectra, (Reasemberg and Oppenheimer 1985). respectively Constant stress-drop lines are indicated by The P- and S-displacement spectra from dashes lines.. Middle figure. Source radius vs Seismic velocity and acceleration sensors have been moment. Radii are computed according to the Madariaga(1976) circular crack model. Bottom figure. Static inverted using the non-linear Levenberg- stress drop vs seismic moment, with source radii computed Marquardt least-square algorithm for curve using the Madariaga source model. Static stress drop values fitting and assuming the Boatwright’s (1980) using the Brune(1970) source radius are a factor 4.5 smaller spectral model. The anelastic attenuation than the ones plotted in the figure. A violation of self- effect is accounted by a constant Q attenuation similarity is observed for events with seismic moment < 1e12 Nm. This is related to the saturation effect of corner operator in the frequency range 0.5-40 Hz, frequency measurement for frequencies higher than about since preliminary analyses have shown that 20-30 Hz the frequency dependent Q models does not provide a significant misfit improvement. To get more robust estimations of the attenuation parameter, a two-step inversion procedure is applied to the S-displacement spectra between 0.5 Hz and 30 Hz. In the first step the spectra are inverted to estimate the t*=T/Q parameter for each source-receiver couple, as well as the event- average estimations of low-frequency spectral level Ωo and corner frequency ωc. In the second step, Ωo and ωc are fixed at the previous found average values, and only t* is inverted. The results of research activity in this work package fall into three categories. The first is the data set itself: the combination of automatic detection tools, with the visual inspection of the helicorders, and a manual re-picking and validation, results into an unprecedented (and still growing) database of micro-earthquakes in the magnitude range [0.5-3.5] which constitutes an outstanding tool for studying the Irpinia fault processes during its interseismic period. The second category is the region modeling. We obtained a 1D velocity model constrained by well- registered events, with a dense coverage of the fault region. The model comprises station corrections, which account for the lateral 3D variations and are compatible with the known structural setting of the area. Moreover, the study of the source spectra, provided site amplification curves for each station and a model of attenuation for P and S waves, which can be described by the following relationships:

2 3 t*P(R) = 0.012 (±0.0011) + 6.5e-04 (±8.1e-05) R - 1.1e-05(±1.6e-06) R + 5.2e-08(±9.4e-09) R 2 3 t*S(R) = 0.015 (±0.0028) + 5.7e-04(±2.2e-4) R - 1.03e-05(±4.6e-06) R + 6.0e-08(±2.8e-08) R where t* is the path anelastic attenuation parameter (t* = travel time / quality factor) (in sec) and R is the hypocentral distance (in km). The third category of results is the accurate determination of the earthquake locations and source parameters. The hypocentral locations (fig 1) show that the seismicity mainly occurs along a pre-existing fault system which is the cause for large earthquakes in this region of southern Apennines. Most of the seismicity can be associated to the complex fault system responsible for the 1980 M 6.9 earthquake and 1990 M 5.7 Potenza earthquake. This observation is further supported by the fault-plane solutions (fig. 1), which show a normal component faulting (pure normal fault and normal fault with a strike-slip component) according to the NE-SW extensional tectonics of the Southern Apennines. This pattern is very consistent with stress orientations inferred by past moderate to large magnitude earthquakes occurred in the area during last few decades. The study of the scaling of source parameters (corner frequency, static stress drop, source radius, fig. 2) with the seismic moments shows, for smaller magnitudes (Mw < 1.5), an abrupt slope change which appears as a violation of the self-similar scaling, but it is likely due to unmodeled attenuation effects at high frequencies. This effect is clearly visible from the plot of corner frequency vs. seismic moment, showing a nearly constant corner frequency for Mo < 1e12 Nm. The plot of static stress drop vs. seismic moment confirms the transition at Mo about 1e12 Nm, above which the static stress drop is nearly constant with a value of 9 MPa (Madariaga circular fault model). The mean value of Brune's stress drop is about 1.7 MPa. The ratio between corner P- and S- corner frequencies (about 1.5) well agree with the expected value from the theoretical crack model of Madariaga,1976. Stress release estimates from corner frequencies (static stress drop) and from integrals of squared velocity spectra (apparent stress drop) show a consistent correlation over three order of moment scale, but with the apparent stress a factor about 100 smaller that static stress. The apparent stress shows a variation with moment similar to the static stress drop, with a slope change at about Mw 1e12 Nm and a nearly constant stress drop scaling at larger magnitudes. We observe that the Hanks & Kanamori ‘ moment magnitude relationship is valid for M>2, while for smaller magnitudes ML generally underestimates the moment magnitude Mw. We interpret this effect as related to the changes in the corner frequency scaling vs seismic moment for Mo < 1e12 Nm.

Workkpackage 3.3: Reflection seismology applied to micro-earthquake data (WP Responsible: Nils Maercklin) In this work package processing methods as in exploration seismology are developed and applied to local micro-earthquakes, aiming toward a 3-D structural image of the crust in the greater Irpinia region. Of particular interest are the reliable identification of reflected/converted waves and of direct S-wave arrivals, which are required for more accurate hypocentral locations (in cooperation with WP3.2). Applied methods include polarization analyses, multichannel processing and moveout corrections of trace gathers, array beamforming or migration for reflected/converted events as well as for the earthquake sources themselves, and first-arrival tomography to obtain a 3-D velocity model. Local earthquake data for this study come from the ISNet seismic network and additional INGV stations in the area (routine operation since 12/2007, additional data 08/2005–11/2007). Detailed quality control ensures validity of a common set of event meta data. The waveform data are available in binary SAC format, including hypocentral information and arrival time picks. Data gathering, multichannel processing, and seismic imaging applications are done with the CWP/SU Seismic Unix exploration seismic software package. A data format converter has been implemented to construct multi-component trace gathers efficiently. Previously developed codes for array beamforming or migration of surface seismic data have been modified for acquisition geometries with sources and receivers at arbitrary depths. These codes have been tested successfully on a limited data set of local and near-regional events. Newly developed and extensively tested processing tools for SAC data feature 3-C trace rotation, polarization analysis based on the time- domain covariance matrix, and polarization filtering. By-products of the software development phase are utilities to manipulate SAC headers, and experimental codes

Figure 3: Seismic common-receiver gather of horizontal-component amplitudes for station RDM3 for first-arrival (left) and horizontal slice through the preliminary 3-D P-velocity model at 3 km depth (right). The picking. seismic traces are aligned at the first P onset (0.0 s) and sorted by hypocentral distance. A Polarization analysis polarization filter to enhance direct S-wave arrivals has been applied. The slope of the coherent first S-wave arrival indicates a Vp/Vs ratio of 1.85, and the delay relative to the theoretical arrival time helps to identify and (red line) is due to low velocities in the vicinity of the station. Within the resolved volume the enhance different velocity structure at 3 km depth shows low velocities (red) in the NE and high velocities in the SW seismic phases by (green). Most events at this depth (dots) occur along the boundary between the two domains, following the trend of the Apenninic fault system. Coordinates: UTM in km, zone 33. utilizing the vector properties of the recorded wave field. Direct P- or S-waves show a high degree of linear polarization in contrast to noise and secondary arrivals. Direct P-waves have steep incidence angles, and corresponding S- waves are polarized perpendicularly to the P-wave direction. These properties are used to construct a characteristic function e.g. for S-waves to guide picking or to be applied as a gain function to enhance S-wave arrivals. Similar polarization filters can be designed for other phases. A complementary approach to identify phases is to employ their lateral coherency in multichannel trace gathers. Different wave types have a different slowness, and moveout and stacking methods

are applicable to further enhance certain phases. An example of a common receiver gather is shown in Fig. 3 (left). These horizontal-component amplitude traces are computed after polarization filtering for S-waves. For details refer to the figure caption. The seismic imaging methods are based on array beamforming and diffraction stack migration.

Essentially, travel times or time delays are computed for the desired phase and for a dense grid of image points in the target volume. The (weighted) stack amplitude or semblance computed along the computed time curve is assigned to the respective image point, and the stack maximum indicates the origin of the phase. This general approach applicable to scattered and reflected/converted waves, as well as for seismic source locations. Triggered by the April 2009 L’Aquila earthquake, much work on this topic has been redirected toward source imaging. Results of an extended source image of this event from ISNet data have been submitted for publication in BSSA, together with contributions of the DPC-S3 project. First arrival times from well-located local earthquakes have been inverted for a 3-D velocity model for the upper crust in the Irpinia region (Vp and Vp/Vs), starting from an initial 1-D model. Forward travel times are computed using an Eikonal solver, and rays are traced backwards through the travel time fields. The inversion for hypocentral locations and velocities is done via an iterative linear least-squares algorithm. Additional arrival picks, refined by cross-correlations, and double difference tomography will be used to improve event locations and velocity model. A depth slice through the preliminary P-velocity model is shown in Fig. 3 (right).

Task 4 - L’Aquila fault system test-site (Task Responsible: Alessandro Amato) The work objectives pursued by our RU within Task 4 have been:

- selection, formatting and creation of the acceleration waveform data-base of the April 6, Mw 6.3 Central Italy (L’Aquila) aftershock sequence recorded by DPC (RAN) and INGV (temporary stations) networks during the period March 30 – April 30, 2009 - determination of L’Aquila aftershock source and attenuation parameters from the non-linear inversion of displacement spectra and preliminary evaluation of source parameter scaling law - inferences on source parameters and kinematic rupture model of the L’Aquila mainshock from the analysis of accelerograms recorded at 250 km distant array (ISNET)

Workpackage 4.3: Estimates of source and structure parameters from seismic waveform analyses (WP Responsible: Pasquale De Gori)

The objective of this work is the estimation by using spectral techniques of the main attenuation and source’s parameters (seismic moment, source radius and stress release) of the L’Aquila earthquake sequence. In S5 project an accelerometric waveform archive of 605 earthquakes recorded between 30 March 2009 and 30 April 2009 by DPC-RAN (National Accelerometric Network) (35 stations) and by INGV (29 stations) permanent and temporary seismic networks has been formatted and compiled (Deliverable 6b). The total number of analysed three-component records is 32275 for events with local magnitude ranging between 2.5 and 5.9. This events are recorded by 3 to 41 stations over a range of distances ranging from near-source (≤ 20 km) to the far-field (100 km). The S-displacement spectra from acceleration sensors have been inverted using the non-linear Levenberg-Marquardt least-square algorithm for curve fitting and assuming the Boatwright (1980)’ spectral model. The analysis of the displacement spectra has been performed on preliminary selected traces with a high signal to noise ratio. The anelastic attenuation effect is accounted by a

constant-Q , attenuation operator in the frequency range 0.5-40 Hz, since preliminary analyses have shown that the frequency dependent Q-models (having the form Q(f)=Qo f^n) do not provide a significant misfit improvement. The optimal Q-model is chosen according to the minimum of the Akaike Information Criterion. To get more robust estimations of the attenuation parameter, a two step inversion procedure is applied to the S-wave displacement spectra in the frequency range 0.05-25 Hz. In the first step the spectra are inverted for estimating the t* parameter (t*=S-wave travel-time/S-wave quality factor) for each source-receiver couple, as well as the event-average estimations of the low-frequency spectral level Ùo and corner frequency ùc. In the second step the spectral inversion is performed fixing Ùo and ùc at the previous found average values providing with estimation of parameter t* only. The attenuation is well described by following relationship t*(R) = -0.013 (+/- 0.006) + 2.50e-03 (+/- 0.4e-03) R – 4.0e-05 (+/-0.8e-05 ) R2 + 2.2e-07 (+/- 0.4e-07) R3 where R is hypocentral distance in km. More robust estimations of Ùo and ùc, are obtained by inverting the displacement spectra fixing for each record the attenuation parameter t* as computed from the formula above. Using the retrieved corner frequencies and the Madariaga (1976) crack model to get the source radius, we computed the variation of the source radius and static stress release with seismic moment. The results show a nearly constant stress drop scaling of source parameters (earthquake self-similarity) within about four orders of magnitude for the seismic moment. The average Madariaga static stress drop is about 35 MPa, which corresponds to a Brune's stress drop of about 6 MPa. The latter is given for comparison with previous stress drop estimations in this and other similar tectonic regions of Italy. Although preliminary (no correction of spectra for site response is applied), this result confirms the evidence for a relatively high value of the average static stress release in this region of Central Apennines relative to the world average (Brune stress- drop around 3-5 MPa) and similar estimations in southern Apennines (Brune stress drop of 2-3 MPa) at the Irpinia fault system test-site, also obtained in this project. The retrieved source parameters are provided with deliverable D6 using a minimum of six records per event. The MW = 6.3 L’Aquila earthquake, on April 6, 2009 has been recorded by the Irpinia Seismic Network (ISNet) about 250 km south-east of the epicenter. Up to 19 three-component accelerometer stations could be used to infer the main source parameters with different seismological methods. We obtained a coarse location of the event from arrival times and array-based backazimuth measurements and estimated the local magnitude (6.1) from an attenuation relation for southern Italy. Assuming an omega-square spectral model we inverted S-wave displacement spectra for moment magnitude (6.3), corner frequency (0.33 Hz), static stress drop (2.5 MPa) and apparent stress (1.6 MPa). Waveform modeling using a point source and an extended source model provided consistent moment tensors with a centroid depth around 6 km and a prevalently normal fault plane solution with a dominant directivity toward south-east. The relatively high corner frequency and an overestimated moment magnitude of 6.4 from moment tensor inversions are attributed to the rupture directivity effect. To image the rupture geometry we implemented a beamforming technique that back-projects the recorded direct P-wave amplitudes into the earthquake source region. A NW-SE striking rupture of 17 km length is imaged, propagating with an average velocity up to 3 km/s. This value is significantly higher than our more realistic estimate of 2.2 km/s from S-wave spectra. Our case study demonstrates that the use of array techniques and a dense accelerometer network can provide quick and robust estimates of source parameters of moderate-size earthquakes located outside the network.

Related publications

Boatwright, J., 1980. A spectral theory for circular seismic sources; simple estimates of source dimension, dynamic stress drop, and radiated seismic energy, Bull Seism. Soc. Am. 70, 1-27. Chatelain, J. L., 1978. Etude fine de la sismicite´ en zone de collision continentale a` l’aide d’un re´seau de stations portables: La region Hindu-Kush-Pamir, These de 3 e´me cycle, Universite´ de Grenoble, Grenoble, France. Hermann, R. B. and C. J. Ammon, 2002. Computer Programs in Seismology version 3.20: Surface Waves, Receiver Functions, and Crustal Structure, St. Louis University, Missouri. Kissling E., Ellsworth W.L., Eberhart-Phillips D. and Kradolfer U., 1994. Initial reference models in local earthquake tomography. J. Geophys. Res., 99, 19635-19646. Lomax, A., J. Virieux, P. Volant and C. Berge, 2000. Probabilistic earthquake location in 3D and layered models: Introduction of a Metropolis-Gibbs method and comparison with linear locations, in Advances in Seismic Event Location Thurber, C.H., and N. Rabinowitz (eds.), Kluwer, Amsterdam, 101-134.. Madariaga R., 1976. Dynamics of an expanding circular fault, Bull. Seism. Soc. Am. 66, 639-667 Reasemberg and Oppenheimer, 1985. P. Reasemberg and D. Oppenheimer, FPFIT, FPPLOT and FPPAGE: Fortran computer programs for calculating and displaying earthquake fault-plane solutions. US Geol. Surv. Open File Rep. 85 739 (1985), p. 109. Waldhauser, F., and W. L. Ellsworth, 2000. A double-difference earthquake location algorithm: Method and application to the northern, Hayward fault, California, Bull. Seismol. Soc. Am., 90, 1353– 1368

Deliverables

# Description Type Authors Restrictions Contact person Relevance D18 Green’s function database Feasibility of from ambient seismic using seismic

noise for the ISNet noise to determine D G.Festa [email protected] network (Irpinia test-site) velocity models none and monitor health state of stations D19 Resolution analysis for the Investigate the cross-correlation limits of

technique at high applicability of the R G. Festa [email protected],.it frequency seismic noise none cross-correlation method D20 Refined re-picking arrival Refined estimates time catalogue and of arrival times D C. Satriano none [email protected] earthquake locations and eqk locations (Irpinia test-site) D21 Parametric catalogue of Refined estimates micro-earthquakes of source and including source D C. Satriano none [email protected] attenuation parameters (Irpinia test- parameters. site) Scaling laws. D22 Digital 3 D velocity model Small scale 3D P- including interface and N. and S- velocity NM none [email protected] event re-location (Irpinia Maercklin model for eqk test-site) location. DAQ6 Report on the refined Refined estimates estimates of source and of source and attenuation parameters attenuation inferred from the analysis R/D A.Orefice none [email protected] parameters. of aftershock records of Scaling laws. the L’Aquila 2009 earthquake sequence

DAQ6b Strong motion data base For RAN, a Earthquake source of L’Aquila aftershock data subset parameters and sequence (RAN and will be scaling law. D A.Orefice [email protected] INGV networks) distributed Refined ground through motion prediction ITACA equations

Problems and difficulties

WP3.1 Difficulties arose from the reconstruction of the dispersion curves for all couples in the frequency range 0.1-0.5. Because of the vicinity of stations (d<20km), causal and anti-causal surface waves do not completely separate at such frequencies. For obtaining the 1d velocity model, we restricted the interpretation to only 4 couples. WP3.3 During the course of this project, software tools and processing procedures for phase identification and imaging with micro-earthquake data have been developed. Processing methods and seismic source imaging have been applied successfully, but a structural image of the Irpinia region from reflected/converted waves cannot be provided yet. Reliable identification of secondary phases, including direct S-waves, has been more difficult and time-consuming than anticipated, e.g. due to local scattering effects in this complex geological environment. However, the recently improved station corrections and refined hypocentral locations from WP3.2, as well as the accomplished tasks described above will improve the accuracy of ISNet event locations and the applicability of migration techniques to image subsurface structures in the region. Due to these difficulties the deliverable D23 (Catalogue of reflected/converted phase arrival times from micro- earthquake data) is not available at the end of the project.

Publications Bobbio A., Vassallo M., Festa G., 2009. A local magnitude scale for southern Italy, Bull Seis. Soc. Am., Vol. 99, No.4, 2461–2470, 2009 doi: 10.1785/0120080364 Convertito V., Iervolino I., Herrero A., 2009. Importance of mapping design earthquakes: insights for Southern Apennines, Italy, Bull. Seis. Soc. Am., Vol.99,N.5,2979–2991,2009, doi: 10.1785/0120080272 Convertito V. et al., 2009. Rapid estimation of ground-shaking maps for seismic emergency management in the Campania Region of southern Italy, Natural Hazard, doi: 10.1007/s11069- 009-9359-2. Festa G., Zollo A., Lancieri M., 2008. Earthquake magnitude estimation from early radiated energy, Geophysical Research Letters, 35, L22307, doi:10.1029/2008GL035576 Cultrera G., Pacor F., Franceschina G., Emolo A. and Cocco M, 2008. Directivity effects for moderate-magnitude earthquakes (Mw 5.6-6.0) during the 1997 Umbria-Marche sequence, Central Italy, Tectonophysics, doi: 10.1016/j.tecto.2008.09.022 De Matteis R., Romeo A., Pasquale G., Iannaccone G., Zollo A.,2010 3D tomographic imaging of the southern Apennines (Italy): a statistical approach to estimate the model uncertainty and resolution, Studia Geophysica et Geodaetica, in press Elia L., Satriano C., Iannaccone G., 2009. SeismNet Manager - A web application to manage hardware and data of a seismic network, Seismological Research Letters, Vol.80, 3. Iannaccone G. et al., 2009. A prototype system for earthquake early-warning and alert management in southern Italy, Bulletin Earthquake Engineering, 2009, doi: 10.1007/s10518-009-9131-8

Lancieri M. and Zollo A., 2009. Simulated shaking maps for the 1980 Irpinia earthquake, Ms 6.9: Insights on the observed damage distribution, Soil Dynamics Earthquake Engineering, doi: 10.1016/j.soildyn.2009.01.007 Lancieri M., Zollo A., 2008. A bayesian approach to the real time estimation of magnitude from the early P- and S-wave displacement peaks, Journal of Geophysical Research, vol. 113, B12302, doi:10.1029/2007JB005386. Maercklin N., Zollo A., Emolo A. and Zahradnik J., 2009. Rupture Directivity Enhanced Mw6.3 Central-Italy Earthquake Damages, Science, submitted N. Maerckiln, A .Zollo, 2009. Estimation of elastic contrasts in a layered model from seismic PS-to- PP amplitude ratios, Geophysical Journal International, 179, 1617-1629, 2009,doi: 10.1111/j.1365-246X.2009.04350.x Maercklin, N., Zollo, A., 2009. Estimation of elastic contrasts in a layered model from seismic PS- to-PP amplitude ratios. Geophys. J. Int., 179: 1617-1626. Maercklin, N., Zollo, A., Orefice, A., Festa, G., Emolo, A., De. Matteis, R., Delouis, B., Bobbio, A., 2010. Source parameters of the April 2009 L'Aquila earthquake, Italy from a distant accelerometer array. Paper submitted to Bull. Seism. Soc. Am. in May 2010. Maercklin, N., Zollo, A., Orefice, A., Festa, G, Emolo, A., De Matteis, R., Delouis, B., Bobbio, A., 2009. The April 2009 Central Italy (L'Aquila) event as seen by a 250 km distant accelerometer array. In: EOS Trans. Am. Geophys. Un., 90. Fall Meeting Supplement, abstract U23A-0021. Maercklin, N., Zollo, A., Orefice, A., Festa, G, Emolo, A., De Matteis, R., Delouis, B., Bobbio, A., 2009. The April 2009 L'Aquila earthquake as seen by a 250 km distant accelerometer array. Poster presented at DPC-INGV 2007-09 Annual Meeting of Seismological Projects, Roma, Italy, Oct. 19-21. Stabile T.A., De Matteis R., Zollo A., 2009. Method for rapid high-frequency seismogram calculation, Computer and Geosciences, Vol. 35, 2, 409-418, doi: 10.016/j.cageo.2008.02.030 Zollo A.et. al., 2009. The earthquake early warning system in southern Itlay: methodologies and performance evaluation, Geophysical Research Letters, Vol. 36, L00B07, doi:10.1029/2008GL036689 Zollo A. et. al., 2009. Earthquake Early Warning System in Southern Italy, Encyclopedia of Complexity and System Science, 5, 2395-2421, 2009, doi 10.1007/978-0-387-30440-3 Zollo, A., Amoroso O., Lancieri M., Wu Y-M., Kanamori H., 2010 A Threshold-Based Earthquake Early Warning Using Dense Accelerometer Networks, Geophys. J. Int., submitted

Book Chapters Martino C, Di Crosta M., Weber E., 2010. Infrastruttura della rete sismica ISNet, in “Metodi e tecnologie per l’early warning sismico”, Eds G. Iannnaccone e A. Zollo, Doppiavoce, Napoli. Satriano C., Di Crosta M., 2010. Software di base per la gestione e l’analisi dei dati, in “Metodi e tecnologie per l’early warning sismico”, Eds G. Iannnaccone e A. Zollo, Doppiavoce, Napoli. Elia L., Satriano C., Martino C., Iannaccone G., Festa G., 2010. Applicazioni software per la gestione della rete ISNet e dei suoi prodotti, in “Metodi e tecnologie per l’early warning sismico”, Eds G. Iannnaccone e A. Zollo, Doppiavoce, Napoli. Vassallo M., Cantore L., 2010. Analisi del rumore sismico, in “Metodi e tecnologie per l’early warning sismico”, Eds G. Iannnaccone e A. Zollo, Doppiavoce, Napoli. Cantore L., Convertito V., 2010. Stima della risposta sismica locale per la regione Campania- Lucania (Appennino meridionale), in “Metodi e tecnologie per l’early warning sismico”, Eds G. Iannnaccone e A. Zollo, Doppiavoce, Napoli. Vassallo M., Satriano C., Di Crosta M., 2010. Identificazione automatica degli eventi sismici alla rete ISNet, in “Metodi e tecnologie per l’early warning sismico”, Eds G. Iannnaccone e A. Zollo, Doppiavoce, Napoli.

Bobbio A., Vassallo M., Festa G., Orefice A., Zollo A., Convertito V., 2010. Calcolo della magnitudo, in “Metodi e tecnologie per l’early warning sismico”, Eds G. Iannnaccone e A. Zollo, Doppiavoce, Napoli. Stabile T.A., Bobbio A., Corciulo M., Satriano C., 2010. Diffusione e accesso ai risultati dell’elaborazione dati, in “Metodi e tecnologie per l’early warning sismico”, Eds G. Iannnaccone e A. Zollo, Doppiavoce, Napoli. Convertito V., De Matteis R., Cantore L., Caccavale M., Iannaccone G., Zollo A., Emolo A., 2010. Gestione del post evento sismico: mappe di scuotimento del suolo, in “Metodi e tecnologie per l’early warning sismico”, Eds G. Iannnaccone e A. Zollo, Doppiavoce, Napoli.

Conference Presentations Convertito V. et. al., 2009. From the rupture to the buildings: reconciling engineering evidences of the April 6 2009 L’Aquila earthquake (Mw 6.3). AGU Fall Meeting, San Francisco, USA, 14- 18 December, 2009. Festa G. and Zollo A., 2009. Early radiation and final magnitude: insights from source kinematics, The 2nd International Workshop on Earthquake Early Warning, Kyoto, Japan Festa G., A. Emolo, E. Lucca, V. Convertito, J. Zahardnik and A. Zollo, 2009. Near source - near field signatures: the April 6, 2009 L’Aquila earthquake French-Japanese Workshop on Earthquake Source, Paris-Orléans, France 5-9 October Iannaccone G., Zollo A. et. al., 2009. PRESTo: a new stand-alone software tool for earthquake early warning, The 2nd International Workshop on Earthquake Early Warning, Kyoto, Japan. Iannaccone G., Zollo A., Satriano C. et. al., 2009. The Irpinia Sesimic Network (ISNet): hardware and data management, EGU General Assembly, Vienna, Austria Maercklin N., Zollo A., Orefice A., Festa G., Emolo A., De Matteis R., Delouis B. and Bobbio A., 2009. The April 2009 L'Aquila earthquake as seen by a 250 km distant accelerometer array, Poster presented at DPC-INGV 2007-09 Annual Meeting of Seismological Projects, Roma, Italy, Oct. 19-21. Maercklin N., A. Zollo, A. Orefice, G. Festa, A. Emolo, R. De Matteis, B. Delouis, A. Bobbio, 2009. The April 2009 Central Italy (L'Aquila) event as seen by a 250 km distant accelerometer array, AGU Fall Meeting, San Francisco, USA, 14-18 December. Matrullo E., Pasquale G., Satriano C., De Matteis R. and Zollo A., 2009.- Building 1D reference velocity model of the Irpinia region (Southern Apennines): microearthquake locations and focal mechanisms The April 2009 L'Aquila earthquake as seen by a 250 km distant accelerometer array, Poster presented at DPC-INGV 2007-09 Annual Meeting of Seismological Projects, Roma, Italy, Oct. 19-21. Orefice A., Zollo A. and Convertito V., 2009. Microearthquake source and attenuation parameters in southern Apennines from the non-linear inversion of P and S- displacement spectra, Poster presented at DPC-INGV 2007-09 Annual Meeting of Seismological Projects, Roma, Italy, Oct. 19-21. Satriano C., M. Lancieri, G. Festa and A. Zollo, 2009. PRESTo: an evolutionary and probabilistic approach to regional earthquake early warning, French-Japanese Workshop on Earthquake Source, Paris-Orléans, France 5-9 October. Satriano C., L. Elia, C. Martino, M. Lancieri, A. Zollo, G. Iannaccone, 2009. The earthquake early warning system for Southern Italy: concepts, capabilities and future perspectives, AGU Fall Meeting, San Francisco, USA, 14-18 December. Stabile T.A., De Matteis R., Zollo A. and Emolo A., 2009. COMRAD: a dynamic ray-tracing algorithm for rapid multi-phase seismogram computation, EGU General Assembly, Vienna, Austria

Satriano et al. 2009. Earthquake Early Warning: System performance and application design, International Workshop on Real Time Seismology: Rapid Characterization of the Earthquake Source and of its Effects, Erice, Italy, May 2-8. Vassallo M. and Bobbio A., 2009. Ambient noise levels and seismic detection threshold of ISNet network, Southern Italy, Poster presented at DPC-INGV 2007-09 Annual Meeting of Seismological Projects, Roma, Italy, Oct. 19-21. Zollo A., 2009. The earthquake early warning system in Southern Italy: technologies, methods and performance evaluation, The 2nd International Workshop on Earthquake Early Warning, Kyoto, Japan. Zollo A., 2009. Lectures on “Real time processing and seismic alert with examples of their implementation”, IASPEI Summer Training School, General Assembly, Cape Town, South Africa, 10-16 Gennaio Zollo, A., Festa, G., Maercklin, N., Satriano, C., Amoroso, O., Bobbio, A., Iannaccone, G., Matrullo, E., Orefice, A., Stabile, T. A., Vassallo, M., 2009. RU S5/6 DSF-UniNA: Research activities in the frame of the S5 project. Poster presented at DPC-INGV 2007-09 Annual Meeting of Seismological Projects, Roma, Italy, Oct. 19-21. Zollo A., Iannaccone G. et. al., 2008. Performance test of earthquake early warning system in southern Italy, ESC – XXXI General Assembly, Crete, Greece, 7-12 September Zollo A, O. Amoroso, M. Lancieri, 1, Y. Wu, H. Kanamori, 2009. An integrated regional and on- site early warning approach: off-line application to the Mw 6.3, 2009 Central Italy (L’Aquila) earthquake, AGU Fall Meeting, San Francisco, USA, 14-18 December Zollo A. et al., 2010. Scaling relations for earthquake source parameters down to decametric fracture lengths in southern Apennines, Presentation at DPC-INGV 2007-2009 Final Meeting of the Seismological Projects, Rome, Italy, 30 June-2 July.

Section 2: S5 Task4 L’Aquila test site Report on the project by UR 7 –A. Amato

UR 7 The role of UR 7 in the project has been both technological and scientific. The goal of UR7 (CNT, Centro Nazionale Terremoti, i.e. National Earthquake Center) was to improve existing networks, make seismic data well organized and easily accessible, use the data to obtain robust hypocentral locations and test hypotheses on variations in time of crustal properties deduced from seismological data (Vp/Vs and anisotropy). The network coverage (both seismic and GPS) has been optimized to map post-seismic deformation and seismicity migration in the months after the main shock of April 2009, in order to identify possible hints of activation of adjacent faults. During this period, concern had raised for both the northern (Reatino) and the southern (Frusinate) regions, where increased seismicity rates were observed thanks to the improved monitoring system. Mapping variations of crustal properties, likely linked to fluids in the crust, revealed an interesting tool to understand the preparatory process of earthquakes.

RESULTS

WP4.1 Toward a permanent Seismic and GPS network to monitor segments adjacent to Paganica fault. Responsible: Gianpaolo Cecere, CNT-INGV [email protected]

The seismic and GPS temporary stations (Fig. 4.1.1 and Tab 4.1.1a,b), installed a few hours after the 6 th April Aquila earthquake, were tuned in order to better follow the post-seismic deformation and to map possible migrations of the seismic activity to the edges of the L’Aquila fault system. In particular we have optimized recording sites with a solar panel stake, a box to host the receiver and the sensor, and a GPRS/UMTS modem to transmit data in real time to INGV headquarters, and fences to protect the whole site (see Deliverable DAQ -1 e D AQ -2).

Fig. 4.1.1 Map of Seismic and GPS temporary stations

Four Character ID Date Installed Monument Description Network - Agency (Site Name) ROPI (Roio Piano) 07 aprile 2009 Wyatt/Agnew drilled-braced RING – INGV CONI (Collebrincioni) 08 aprile 2009 Wyatt/Agnew drilled-braced RING – INGV SGRE (San Gregorio) 15 aprile 2009 Wyatt/Agnew drilled-braced RING – INGV CAPE (Capestrano) 16 aprile 2009 Wyatt/Agnew drilled-braced Ufficio SISM – DPC LEOF (Leofreni) 17 aprile 2009 steel rod ISPRA Table 4.1.1a: GPS temporary stations

ID (Site Name) Date Installed Sensor Acquisition system T0104 (Coppito) 09 /10/2009 Vel. TRILLIUM-120C Satellite - Nanometrics T0104 (Coppito) 09 /10/2009 Acc. Episensor FBA ES-T Satellite - Nanometrics T0106 (Roio Piano) 11 /10/2009 Vel. Lennartz LE3D-1S Satellite - Nanometrics T0107 (San Pelino) 21 /05/2009 Acc. Episensor FBA ES-T Satellite - Nanometrics T0110 (Coppito) 02 /09/2009 Acc. Episensor FBA ES-T Satellite - Nanometrics SMA1 (San Martino) 13/08/2009 Vel. Lennartz LE3D-5S UMTS- GAIA2 Table 4.1.1b: Seismic temporary stations. Note that there are both broad-band seismometers, short period and strong motion sensors. Preliminary GPS data analysis (Fig. 4.1.2) shows an evident post seismic signal, mostly revealed by stations CONI, ROPI and SGRE, installed in the days immediately after the main shock. In particular, observing the plots in Figure 4.1.2 (particularly that of station CONI, one of the first installed stations), we note that the first period shows a strong horizontal motion mostly visible on the N-S component, due to after-slip phenomena on the fault plane (Cheloni et al. 2010). Post seismic movements continue for several months, decreasing gradually of intensity. Other analyses of post seismic movements in that area are described in Cheloni et al. (2010). This evidence of post seismic signal would be completely lost without this type of intensification of GPS network in the epicentral area. Data are stored at: http://bancadati.gm.ingv.it and made available under request.

Fig. 4.1.2 Time series of the 5 GPS stations installed. The orange line shows the 2009, April 6th earthquake. The seismic stations installed in this WP (Table 4.1.1b) have been and are being used during the project time frame by the National Seismic surveillance system, as an integration to the permanent national network (RSN). These data are archived and available together with RSN station seismograms at INGV ( http://eida.rm.ingv.it/ ). During this period, data from these semi-permanent stations have contributed to the hypocentral locations for many hundreds of local and regional earthquakes, lowering significantly the detection threshold in the region (see http://iside.rm.ingv.it )

Figure 4.1.3 Comparison between epicentral locations in the L’Aquila region for earthquakes with M>=1.8 (left) using the completeness threshold in central Italy, and all located earthquakes (right). The period is from 1/1/2010 to 9/6/2010. The numbers of plotted events is 200 and 1221, respectively.

WP4.2: Integrated SEED seismic database of L’Aquila sequence Responsible: Aladino Govoni CNT- INGV [email protected]

All the continuous data recorded by the 18 mobile stations operated by INGV/CNT and the 3 mobile stations operated by INGV/CT deployed during the L'Aquila sequence (figure 4.2.1) have been completely qualified, converted to SEED data format and made available to the scientific community at http://dpc-s5.rm.ingv.it/en/Database-AquilaFaultSystem.html using the EIDA platform (European Integrated Data Archive http://eida.rm.ingv.it/ ). Also all metadata available have been checked and converted to SEED format. The EIDA archive gives access also to the National Network data, including semi-permanent stations described in WP 4.1. This data set spans from a few hours after the April 6, 2009 mainshock (first data recorded at 04:43:08 UTC) to March 23, 2010 when the last 9 stations were closed, and consists of about 270 GB (figure 4.2.2). A total of 30 sites where deployed during this period adapting the network geometry to the evolution of the seismic sequence. This work has been done in steps as the data became available using and further developing the software procedures developed for the Messina test site (WP2.2).

Figure 4.2.1: Map of all mobile seismic stations deployed during the L'Aquila sequence together with all National and regional network stations available at EIDA data center.

Between April and June twenty stations were installed by LGIT (Grenoble, France) with the help of INGV staff. All the data recorded by the seismic stations are distributed in the same SEED format at http://www.fosfore.ipgp.fr/en/ (in "Fosfore Portal" under "Stations", network XJ) together with metadata.

Figura 4.2.2. Data availability of the temporary network stations (from April 6, 2009 to March 23, 2010).

WP4.3: Applications to the database of automated and semi-automated seismic analysis Responsible: Pasquale De Gori CNT- INGV [email protected]

Results a) An automatic and semi-automatic picking modular procedure, developed in the frame of S5 project (WP 1.1), has been applied to L’Aquila seismic waveforms database. This modular procedure includes: - triggering algorithm and events association routine; - P- and S-wave arrival times and polarity identification; - 1D events location and local magnitude determination. Using the seismograms recorded in continuous mode by the permanent INGV network and by the temporary array deployed soon after the 06 April 2009 (h 01.33 UTC) mainshock, the arrival times of 2866 aftershocks with Ml>1.9 have been obtained, collecting 72,829 and 36,229 readings, and polarities for P and S-wave, respectively. In addition, the seismicity preceding the mainshock has been processed on the permanent INGV network, determining the arrival times for 561 events. b) The best starting 1D Vp model and the average Vp/Vs have been computed. We selected a gradient model that accounts for low velocity in sedimentary units outcropping in the study area and high velocity limestones in the upper crust. In detail, the model consists of a Vp that increases linearly from Vo (5.0 km/s) at the surface by 0.15 km/s per kilometre until the half space is reached at a depth of 10 km. The P velocity within the half space is 6.51 km/s. The choice of a gradient model is also to avoid classical artefacts such as fictitious horizontal alignments of seismicity. The mean Vp/Vs is 1.90 and it has been determined on the basis of the cumulative Wadati-diagram. c) The 1D location of seismicity has been used to recover the spatial and the temporal evolution of seismic sequence and to reconstruct the geometry of the normal fault system. In figure 4.3.1 and 4.3.2 we show the distribution of seismicity in map and in some vertical cross-sections. The mainshock, located around 9.3 km of depth, activated a ~50° SW-dipping and ~135° NW-trending normal fault with a length of about 16-18 km. The foreshocks nucleated on the main fault plane and along a minor oblique NS-trending trans-tensional fault located off the main plane. The geometry of the fault is coherent with the mapped San Demetrio-Paganica and Mt. Stabiata normal faults. The seismicity activated the whole fault structure, from 10 km depth up to the surface. A second structure, controlled by a Mw 5.4 event (9th of April - 00:53 UTC) at ~11 km depth, is located to the north and forms a right lateral step with the main fault. This segment is recognisable, NW-trending for about 12-14 km of length, close to the Campotosto Lake. It shows a shallower dip angle of about 35° with a tendency to flattening toward the deepest portion. Due to the lack of seismicity above 5 km depth, the connection between this structure and the mapped Monti della Laga fault is not straightforward. d) Study of the time variation of the Vp/Vs and seismic anisotropy using the foreshock data. We have computed, for each event, the average Vp/Vs following the same approach used in seismic tomography to reconstruct Vp/Vs models at local scale. The clear change of the Vp/Vs ratio during the foreshock sequence suggests that seismic rays travel through a fractured medium, and that fracture field properties vary with time. The observations suggest that diffusion of fluids play a key role in the earthquake preparation process. Differences in the Vp/Vs trend at stations differently located with respect to the fault, help to retrieve the directional properties of the fluid diffusion process and to propose a physical model explaining our observations. Furthermore, the presence of stress aligned micro-cracks or stress opened fluid filled cracks and fractures within the sedimentary cover is detected by studying seismic anisotropy. We observe variations of the anisotropic parameters during the days before the occurrence of the mainshock. Variation of elastic and anisotropic parameters during the preparatory phase of L’Aquila earthquake (figure 4.3.3) demonstrates that a complex sequence of dilatancy and fluid diffusion processes affected the rock volume surrounding the nucleation area.

Problems and difficulties The time requested to read P and S wave arrival times on a huge amount of seismic data has delayed the analysis of Vp/Vs and anisotropy on the aftershocks. We Have only preliminary results for the aftershock sequence that will be presented at the final Conference at the end of June

Figure 4.3.1. Map view of seismicity distribution: red points for foreshocks and black points for aftershocks. The locations (stars) of the larger events (Mw>3.5) of the sequence are reported colour coded by their size. Dark brown lines represent the Quaternary mapped normal faults. The N45E- trending thin lines are the traces of the 52 vertical cross sections (see Figures 2). In yellow we trace also the main surface breakages as mapped by the EMERGEO Working Group. (SDP=San Demetrio Paganiga, CMP=Campotosto)

Figure 4.3.2. Vertical cross sections for the L’Aquila area (in each section we report the hypocentral depth (km) vs. distance (km) of the event projected on the vertical plane). We report with the brown points located at the surface the intersection between mapped fault and cross section traces. Yellow points indicate the intersections between the surface breakage and section traces. We report also the names of the most significant faults and geographic locations (SDP=San Demetrio Paganica).

Figure 4.3.3. Comparison between time series of Vp/Vs and anisotropy parameters at L’Aquila station (AQU). Time is expressed in days starting from 1/1/2009. A): Vp/Vs values at stations AQU. B): Normalized delay time δt. (delay time divided the length of S-ray path). C): Azimuth φ of the fast shear-wave polarization direction. D): Azimuth of shear waves linearly polarized: null directions. On each panel the vertical line represents the occurrence of the ML = 4 foreshock; black circles are the individual measurements; red circles are the mean values; red vertical bars indicate the standard deviation of the mean; green lines are the mean values interpolating functions. The mean values are calculated on running windows of 20 samples with one sample step in panels A and D, and of 5 samples with one sample step in panels B and C.

Deliverables

# description type authors restrictions contact person relevance DAQ1 Five Cecere Data available only to Cecere Gianpaolo High: it additional Gianpaolo the INGV users improved the continuous Abruzzese ftp:\\gpsgiving.gm.ingv.it monitoring GPS stations Luigi during the integrated D’Ambrosio aftershock into the Ciriaco sequence RING De Luca Giovanni Falco Luigi Memmolo Antonino Minichiello Felice Zarrilli Luigi DAQ2 Five Cecere Data available to the Cecere Gianpaolo High: it additional Gianpaolo public improved the seismic Abruzzese http://iside.rm.ingv.it/ monitoring stations with Luigi http://eida.rm.ingv.it/ during the real time De Luca aftershock acquisition Giovanni sequence Falco Luigi Zarrilli Luigi DAQ3 Integrated databank Govoni, Di Data available to the [email protected] High: in this SEED Stefano, public (see text above) archive waveform Chiaraluce, seismic data database Moretti, are available Pintore, to the Lauciani scientific comunity DAQ4 Refined Scientific Chiaraluce, Hypocentral data [email protected] High: it hypocentral paper - L., available under request [email protected] identifies locations of File Chiarabba, faults the seismic (+map C., De Gori, activated sequence and P., Di during the (complete) table) Stefano, R., seismic Improta, L., sequence Piccinini, D., Schlagenhauf, A., Traversa, P., Valoroso, L., Voisin, C DAQ7 Variations in Scientific Lucente, F.P., Articles [email protected] Medium: this time of paper De Gori, P., study structural Marheriti, L., contribute to characteristics Piccinini, D., the (Vp/Vs, Di Bona, M., understanding anisotropy) Piana of the (complete on Agostinetti, seismogenic foreshock N. process data, in progress on aftershocks data)

Publications Cheloni D., N. D’Agostino, E. D’Anastasio, A. Avallone, S. Mantenuto, R. Giuliani, M. Mattone, S. Calcaterra, P. Gambino, D. Dominaci, F. Radicioni, G. Castellini [2010]. Coseismic and initial postseismic slip of the 2009 Mw 6.3 L’Aquila earthquake, Italy, from GPS measurements. Geoph. J. Int., doi: 10.1111/j.1365-246X.2010.045e 84.x

Lucente, F.P., De Gori, P., Marheriti, L., Piccinini, D., Di Bona, M., Piana Agostinetti, N., 2010. Temporal variation of seismic velocity and anisotropy before the 2009 Mw 6.3 L'Aquila earthquake, Italy, 2010. Accepted in Geology

Chiaraluce, L., Chiarabba, C., De Gori, P., Di Stefano, R., Improta, L., Piccinini, D., Schlagenhauf, A., Traversa, P., Valoroso, L. and Voisin, C., 2010. The April 2009 L’Aquila (Central Italy) Seismic Sequence. Submitted to Bollettino di Geofisica Teorica e Applicata

Memmolo A. [2010] Il GPS in emergenza – l’esperienza del terremoto de L’Aquila del 6 aprile 2009 – Rapporto Tecnico INGV in press

Margheriti et al Emergenza “Aquila2009”: La campagna di acquisizione dati della Rete Sismica Mobile stand-alone del Centro Nazionale Terremoti (Re.Mo.) Rapporto Tecnico INGV submitted

Abruzzese et al.[in prep] – La Rete Mobile Telemetrata – Rapporto Tecnico INGV in preparazione

Meetings

Aldersons F., Chiaraluce L., Di Stefano R., Piccinini D., Valoroso L. 2009 Automatic Detection, and P- and S-wave Picking Algorithm: an application to the 2009 L'Aquila (Central Italy) earthquake sequence, Eos Trans. AGU 2009 Fall Meeting, poster sesssion

.Lucente, F. P., De Gori P., ,L. Margheriti et al. 2009 The preparatory phase of the April 6th 2009, Mw 6.3, L’Aquila earthquake: Seismological observations, Eos Trans. AGU, 90(52), Fall Meet. Suppl., Abstract

Moretti, M.; Govoni, A.; Nostro, C. et al. 2009 The new emergency structure of the Istituto Nazionale di Geofisica e Vulcanologia during the L’Aquila 2009 seismic sequence: the contribution of the COES (Seismological Emergency Operation Center – Centro Operativo Emergenza Sismica) Eos Trans. AGU, 90(52), Fall Meet. Suppl., Abstract

Valoroso L., Amato A., Cattaneo M. et al., 2009 The 2009 L'Aquila seismic sequence (Central Italy): fault system geometry and kinematics. Eos Trans. AGU, 90(52), Fall Meet. Suppl., Abstract

Lauro Chiaraluce et al. The 2009 L'Aquila sequence (Central Italy): fault system anatomy by aftershock distribution. (solicited) Vienna, Austria, 02 – 07 maggio 2010 EGU

Report on the Project S5 UR08 by responsible Luigi Improta UR08 gathers a wide range of research activities (earthquake geology, exploration geophysics, statistical seismology) subdivided into three sub-projects. These sub-projects were devoted to: i) the collection of high-resolution shallow seismic profiles across the Middle Aterno Valley (wp 4.4), ii) the accurate mapping and characterization of active faults in the epicentral area (wp 4.5), iii) the production of a feasibility study to improve earthquake forecasting models by incorporating geophysical observables (wp 4.6).

1 - RESULTS OBTAINED IN THE PROJECT FRAMEWORK

WP4.4: Active fault imaging in the Middle Aterno Valley by high-resolution seismic profiling (Luigi Improta and Pier Paolo Bruno)

The primary goal of the research was the collection of high-resolution seismic profiles across the Middle Aterno Valley. Specific targets of the exploration were the Paganica Fault, causative source of the 6 April mainshock, and the Bazzano basin, where the maximum of co-seismic subsidence was observed. Unfortunately, results are limited to the data acquisition and pre- processing because a 5-months delay in the seismic experiment has prevented to complete data processing and to produce reflection stack sections and Vp models by refraction tomography (Deliverables D8, D9, D10). The first phase of research was devoted to the design of the experiment. We focused on the portion of the Middle Aterno Valley extending between Paganica to the north and Civita di Bagno to the south, across the Bazzano-Monticchio ridge (Fig.1a). We analyzed aerial photos, published geologic maps and results of geologic studies, which were going on in the framework of this project (wp 4.5) and of the DPC project for seismic microzonation. However, unfavorable logistic and environmental conditions posed significant difficulties. Main factors hampering seismic surveying are the high urbanization and the presence of a railway, a national road and the Aterno river, which parallel the valley. In particular, main geologic targets are located in correspondence of Paganica and of the Bazzano industrial suburb, affected by significant sources of seismic noise. Temporary construction sites of the C.A.S.E. project located in the survey area posed additional difficulties. As result, we traced five seismic profiles that represent a good compromise between geologic targets and logistic conditions (Fig.1a). Noteworthy, acquisition of profiles P1, P2 and B2 required closing to traffic main roads with the assistance of local authorities and patrol. The profiles had a total length of 6800 m and were acquired by a team of fifteen researchers of the INGV during a ten-day-long experiment in April 2010. Specific geologic targets were: the Paganica Fault (Profile P2), the hanging-wall of the Paganica Fault and NE-dipping antithetic splays (Profile P1), extensional faults bounding the Bazzano-Monticchio ridge (Profile B_R1), the Bazzano basin (Profiles B1 and B2). Data were acquired with a dense, wide-aperture geometry (Table 1). Dense sources (5-10 m), provided by a high-resolution (10-200 Hz) vibroseis (IVI-Minivib of the A.M.R.A. S.c.a.r.l.), were recorded by a 216-multichannel seismograph with a geophone interval of 5 m. The deployment of a 1075 m wide geophone spread, 3-4 times longer than the maximum depth of the pre-quaternary substratum, allowed to densely illuminate the targets by collecting simultaneously: (1) multifold, common-mid-point, near-vertical and wide-angle reflections, (2) dense first arrivals corresponding to turning and refracted waves traveling inside the basins and the substratum. Overall, common shot gathers (CSG) exhibit a good S/N ratio after pre- processing and are highly informative. In the Bazzano basin, prominent wide-angle reflections dominate down to 400 ms, corresponding to an exploration depth of 400-500 m, and first arrivals are readable even at large offset (Fig.1d). CSGs in the Bazzano and Paganica areas contain clear high-frequency near-vertical reflections generated by basin infilling and low-frequency wide- angle reflections from the substratum (200 ms, corresponding to about 200 m depth, in Fig.1c). Asymmetric trends of reflection hyperbola reveal sharp lateral variations and steep-dipping reflections across the Paganica Fault (Fig.1b-c). Preliminary stack sections obtained by rough CDP processing flows provide very promising images of the basins (Fig.1e). Although we have not completed data processing yet, our research has significant relevance because we successfully acquired good-quality shallow seismic data in a challenging urban environment. We believe that stack sections and Vp models will give valuable subsurface constraints to the DPC and scientific community, for a better understanding of: (1) the stratigraphy of the continental deposits infilling the basins and of the shallow architecture of the fault systems, (2) the kinematic interaction between the Paganica Fault and secondary splays, (3) the long-term and recent tectonic evolution of the Middle Aterno Valley, (4) the local site effects observed during the seismic sequence.

Figure 1 : (a) geologic map of the investigated portion of the Middle Aterno Valley with location of the acquired seismic profiles; (b-d) examples of pre-processed common shot gathers with evident deep reflected arrivals from the substratum (down to 400 ms) and shallow reflections from basin strata (< 200 ms); (e) preliminary CDP stack sections across the northern sector of the Bazzano basin (line B2).

Profile Length Geophone Source Max. N° of stacked Ground Data quality (m) spacing (m) spacing (m) Folding sweep

P1 2085 5 10 54 3 paved roads and agricultural fields good

P2 1125 5 5-10 108 3-5 paved roads fairly good

B1 1075 5 5-10 108 3 agricultural fields very good

B2 1495 5 10 54 3-5 paved roads good

B-R1 985 5 10 54 3-5 paved roads and agricultural fields fairly good

Table 1. Field parameters used for seismic profiling

WP4.5: Mapping of active faults and characterizing their seismic behaviour (Francesca R. Cinti and Stefano Pucci)

The results of the WP 4.5 were obtained in three sections: 1) mapping of active faults; 2) characterizing their seismic behaviour; 3) GIS implementation. 1. Mapping of active faults of the L’Aquila test site included 2 steps: 1.1) Definition of the parameters describing an active fault to implement into the database; 1.2) Performing geological and geomorphological investigations of specific faults for their 1:25.000-scale mapping. 1.1) By applying the USGS standards, we integrated parameters according to the requirements of the active tectonic setting of Italy. These parameters include: fault generalities, in order to describe structural and geomorphic features related to the fault activity; detailed location and description of the features used as constrain for the fault activity; paleoearthquakes and slip model data characterizing the fault behavior. Moreover, there are parameter fields appropriate for assessing the hazard associated to the fault, and others describing the ground shaking-related environmental effects. The stage of knowledge of the faults is not homogeneous in the area, so that we assigned a rank to each structure based on the available constraints. This rank is useful to guide future investigations and data acquisition on less constrained active faults. References of each data are absolutely due. This step was relevant: i) for the fault database setting; ii) as guide for the field survey, and iii) to developing for the first time a wide collaboration among researchers of INGV, ISPRA, CNR, DPC, and Universities with expertise in the geological survey and earthquake geology. 1.2) Following the review of the state of the art of the faults knowledge, field and aerial photo surveys were conducted focusing where strong uncertainties and evident lack of data were manifest. Different teams performed geological, geomorphological, and geophysical (GPR and ERT) investigations of specific faults and a map of the active faults was provided as resultant product. The field mapping was conducted at 1:10.000 scale, for a layout at 1:25.000 scale. The map and the fault data collection appear substantially improved respect to the previous compilations. The improvement was obtained in: a) detail of the surface fault trace (e.g. the Paganica fault); b) constraints on the faults activity; c) definition of previously unknown fault parameters (e.g. the S.Pio delle Camere fault); d) recognition of new active faults (e.g. faults in the Montereale Basin). The provided mapping is outstanding, resulting from the decisions taken by numerous earthquake geologist experts operating in the Apennines for years. The results obtained on the location and characteristics of the active faults of the area provide a spin-off for the knowledge of the detailed layout of the fault systems. In particular in this portion of the Aterno River Valley, the understanding of geometrical complexities and fault arrangement evolution through time is crucial to: i) the development of rupture segmentation models; ii) the assessment of the earthquake hazard and the improvement of earthquake forecasting capability; iii) the modeling of earthquake scenarios, including the estimate of surface faulting hazard relative to critical facilities close to the fault escarpments (i.e. water and power lines, schools, transportation and communications systems). 2. Paleoseismic trenching and coring were conducted to characterize the short-term activity (i.e. Holocene) of the faults. Attention was focused on the Paganica fault with the aim of understanding if the 6 April 2009 earthquake is a typical event for this fault. Four paleoseismic sites along the central 3 km of the fault were analyzed. The investigations are based on the identification of deformations affecting the Holocene depositional sequence, correlation of events among trenches, and their dating through C 14 analysis of charcoal and soils, pottery fragments. The main findings can be summarized as follows: (a) the 2009 Paganica surface rupture is directly related to a fault plane at depth, where multiple paleoevents of faulting occurred with similar style of deformation; (b) there are indications for small (0.1-0.3 m) and large (0.4-0.8 m) slip per events occurring prior the 2009; (c) older events seem consistently larger in slip (this latter statement requires additional data if we consider multiple fault strands rupture vs. single punctual observations); (d) the pre-2009 event is likely the 1461 earthquake; (e) the evidence for contemporary rupture of multiple strands like in 2009; (f) the average recurrence of surface faulting is of ~700 yr (5 earthquakes in the last 2800 yr); (g) the Holocene slip rate is of ~0.25 mm/yr, similar to the 0.2-0.3 mm/yr from the last 30 kyr. Moreover, along the central section of the Paganica fault, two more trenching sites were excavated in the framework of the SIGRIS-ASI project ( www.sigris.it ) in the attempt to validate the source models constrained by SAR interferometry analysis of the co-seismic displacement field. The results available for this two sites confirm: (1) the evidence for past seismic events occurring during the Holocene; (2) the slip associated to the penultimate event would be 0.15-0.2 m; (3) the penultimate event possibly occurred in the last millennium based on preliminary dating, with a preferred association by the Authors to the 1703 (XI MCS, M6.7, located northward of the 2009 sequence). Ground Penetrating Radar across the Paganica surface rupture provides a maximum throw-rate of 0.23- 0.30 mm/yr over 15 kyr, comparable with the value given by paleoseismological data. Geological cross-sections of the fault system, GPR profiles and a 30m-deep borehole were also conducted to investigate the long-term (i.e. Pleistocene) activity of the Paganica fault. A minimum long-term slip-rate of 0.25-0.5 mm/yr was estimated on the base of offset Early- Pleistocene lacustrine deposits. 3. The database derived from stages 1 and 2 has been implemented in a Geographic Information System (GIS) using ESRI ArcGIS 9.3 software product, in a personal geodatabase for Microsoft Access 2003 format. The geodatabase hosts both the geometry data and the great amount of associated descriptive information of the fault features, is easy to query and update and has a scalable hierarchical scheme. It is designed to serve a variety of needs, both in terms of the user community and of the methods of delivering the data, and can be used definitively in current and future seismic-hazard analyses. Attributes have been normalized in 5 hiearchical levels of information. The geodatabase contains 3 feature classes: Sections, SectionKeypoints and EnvEffKeypoints. A mask has been create to facilitate the input of collected information and the archived information can be extracted and delivered in different formats such as reports, maps or tabular data.

WP4.6: Toward a new Earthquake Forecast: a multidisciplinary approach (Warner Marzocchi) The main purpose of this research has been to explore the possibility to improve the short-term (large) earthquake forecast capability through a generalization of the available stochastic models and/or the development of new strategies. As reported in the original proposal, our goal has been to prepare a report (Deliverable D15) that will be available for the end of the project. The report contains some clues, thoughts, and general strategies that may guide future researches on this field. According to the planned activities, we have first reported the state of the art in the short-term forecast of large events. Basically, we have identified only few models that are currently used in this field: clustering models (e.g. Epidemic-Type Earthquake Sequences ETES, and Short-Term Earthquake Probability STEP), and the Agnew and Jones' model (Agnew and Jones, 1991). The first class of models is mostly based on the triggering effect of each earthquake that ultimately creates clusters of seismicity. The latter is based on a statistics of foreshocks before a large event. In this respect, during this project (Marzocchi and Zhuang, 2010, in preparation) we have tested if the occurrence of felt foreshocks in the few days before the main L'Aquila event was compatible with the clustering class of models. The results indicate that the short-term foreshock activity was compatible to what expected by an ETES model in Italy. We have also explored past cases in Italy and California, finding that the seismicity preceding the main events is not statistically significant from what expected by the clustering models. For the other activities, we have discussed with many interested colleagues in dedicated brainstorming about the possibility to select and include other kind of precursory signals, or, in general, strategies to improve our present skill in short-term forecast of large events. In the Deliverable D15 we have reported the identified weaknesses of clustering models (practically entirely based on the information contained in seismic catalogs), and a list of possible parameters that might be used to achieve more skillfulness forecasting tools. In the same deliverable, we have looked into possible probabilistic strategies to improve the existing forecasting models (e.g. ETES) and to include expert opinion into forecasts. To this purpose, a careful investigation on the practical and philosophical aspects of using probabilistic forecast produced by models and/or by expert opinion has been also carried out (Marzocchi and Zechar, 2010, in preparation).

2 Deliverables Project S5, UR08

# description Type authors restricti contact relevance ons person D11 List of Excel sheet Vittori, E.; Cinti, No Cinti, Propedeutic for the parameters F.R.; Pucci, S.; F.R.; mapping of active describing Pantosti, D.; Pucci, faults and basis for active faults Vannoli, P.; De S. the Geodatabase Martini, P.M.; Montone, P.; Gori, S. D12a Map of active file *.jpg Cinti, F.R.; Pucci, No Cinti, Improvement of faults S.; Civico, R.; F.R.; previous Pantosti, D.; Pucci, compilations by: a) Vannoli, P.; De S. detail of the surface Martini, P.M.; trace of faults; b) Moro, M.; Gori, constraints on the S.; Falcucci, E.; faults activity; c) Saroli, M.; Galli, definition of P.; Messina, previously unknown P.;Pierdominici, fault parameters; d) S.; Blumetti, A.; recognition of new Chiarini, E.; La active faults Posta, E.; Papasodaro, F.; Fiorenza, D.; Fracassi, U.; Vannoli, P.; Di Bucci, D.; Burrato, P.; Cowie, P.; McCaffrey, K.; Phillips, R.; Roberts, G.; Sammonds, P. D12b Geodatabase files *.gdb; Patera, A. No Cinti, Facilitate the input *.mxd; *.mdb F.R.; and extraction of Pucci, collected and S. archived information; information easy delivered in different formats D13 Log of the files *.jpg; Cinti, F.R.; Pucci, Respect Cinti, New data on the Mo’tretteca Table *.doc S.; Pantosti, D.; of F.R.; seismic behavior of trench and De Martini, P.M.; intellectu Pucci, the Paganica Fault core, ages of Civico, R.; al S. layers, Pierdominici, S.; property interpretation Cucci, L.; Brunori, of the events C.; Pinzi, S. D14 Suggested 1)Trenching Cinti, F.R.; Pucci, No Cinti, Development of future along the S.; Pantosti, D.; F.R.; rupture activities Paganica Fault; De Martini, P.M.; Pucci, segmentation 2)Trenching Civico, R.; S. models for the along other faults Pierdominici, S.; Paganica Fault; of the DB; Cucci, L.; Brunori, 3)Slip rates C.; Pinzi, S. reconstruction at different time scales along the Paganica Fault;

D15 Vision paper Document *.doc Marzocchi, W. Confiden Marzoc The document on possible tial chi, W. reports possible developments guidelines for future of short-term research on short- earthquake term earthquake forecasting forecasting models

3 - PROBLEMS AND DIFFICULTIES Problems and difficulties were encountered by wp 4.4. A 5-months delay in the planned seismic experiment (from November 2009 to April 2010) was caused by: 1) temporary construction sites of the C.A.S.E. project (November-February) in the survey area, which produced a significant increase of the seismic ambient noise; 2) unfavorable weather conditions during winter. Due to this delay, data processing and inversion are still on-going and the planned deliverables (reflectivity and P-wave velocity images of the basins and faults) will be produced after the end of the project.

4 – PUBBLICATIONS

Cinti, F.R., Civico, R., Cucci, L., De Martini, P.M., Pantosti, D., Pierdominici, S., Pucci, S., Brunori, C.A., 2009. Looking for surface faulting ancestors of the l’Aquila April 6, 2009 event: preliminary paleoseismological data and seismic hazard implications. Extended abstract presented at the GNGTS Conference, Trieste, 16 - 19 novembre, Sessione SPECIALE: Il terremoto dell'Abruzzo. Cinti, F.R., Civico, R., Cucci, L., De Martini, P.M., Pantosti, D., Pierdominici, S., Pucci, S., Brunori, C.A., Fracassi, U., Villani, F., 2009. Looking for surface faulting ancestors of the L’Aquila April 6, 2009 event: preliminary paleoseismological data and seismic hazard implications. Eos Trans. AGU, 90(52), Fall Meet. Suppl., Abstract U12A-07. Civico, R., Pucci, S., De Martini, PM., Pantosti, D., Cinti, F.R., Pierdominici, S., Cucci, L., Del Carlo P., Brunori, C.A., Patera, A., Pinzi, S., 2010. Long-term expression of the Paganica Fault vs. 2009 L’Aquila Earthquake surface ruptures: looking for a better understanding of its seismic behaviour. Geophysical Research Abstracts, Vol. 12, EGU2010-12775-1, 2010, presented at the EGU General Assembly 2010. Di Bucci, D., Burrato P., Vannoli P., Fracassi U., Valensise G., 2010. Seismogenic faults and their surface segnature: insights from the 2009 L’Aquila earthquake (Central Apennines, Mw 6.3) for the understanding of adjacent areas. Terra Nova , Submitted Di Bucci, D., P. Burrato, P. Vannoli, U. Fracassi and G. Valensise, 2009. Surface faults, seismogenic sources and their morphotectonic signature: lessons from the 6 April 2009 L’Aquila earthquake and applications to adjacent areas (Middle Aterno). Geoitalia 2009, VII Forum Italiano di Scienze della Terra, 9-11 September, Rimini, Italy. Falcucci E., Gori S., Moro M., Galadini F., A.R. Pisani, and P. Fredi, 2010. Holocene activity of the Subequana Valley-Middle Aterno Valley normal fault system, south of the epicentral area of the April 6, 2009 "L'Aquila" earthquake (Mw 6.3): Implications for seismic hazard in central Italy. Geophysical Research Abstracts, Vol. 12, EGU2010-11622, 2010, presented at the EGU General Assembly 2010. Marzocchi, W., Zhuang, J., 2010. Some clues on the short-term foreshock activity in Italy and California. To be submitted to Geophys. Res. Lett. Marzocchi, W., Zechar, J.D., 2010. Earthquake forecasting/prediction in practice: different attitudes and the selection of the "best" model. To be submitted to Bull. Seismol. Soc. Am. Pantosti, D., Cinti F.R., De Martini P.M., Pucci, S., Civico, R., Pierdominici, S., Cucci, L., Brunori, C.A., Patera, A., Pinzi, S., 2010. Discovering the characteristics of the surface faulting ancestors of the L’Aquila April 6, 2009 earthquake by paleoseismological investigations. Geophysical Research Abstracts, Vol. 12, EGU2010-9673, 2010, presented at EGU General Assembly 2010. Roberts, G.P., Raithatha B., Pizzi A., Pucci S., Walker J.F., Wilkinson M., McCaffrey K., Phillips R., Michetti A., Guerrieri L., Blumetti A.M., Vittori E., Sammonds P., Cowie P., 2010. Shallow sub-surface structure of the 6th April 2009 Mw 6.3 L’Aquila earthquake fault zone at Paganica, investigated with Ground Penetrating Radar. Submitted to Journal of Geophysical Research-Solid Earth.