S11C-1750 The Range-Bounding Fault-System (Southern ): New Evidence of Recent Activity From High-Resolution Seismic Profiling AGU Fall Meeting Castiello A. (1), Villani F. (1), Bruno P.P. (1), Improta L. (1), De Rosa D. (1),Di Fiore V. (2), Punzo M. (3), Varriale F. (1), Montone P. (1), Pierdominici S. (1), Rapolla A. (4) 15-19 December 2008 1 - Istituto Nazionale di Geofisica e Vulcanologia, via di Vigna Murata, 605 - 00143 Rome, Italy; e-mail address: [email protected], [email protected], [email protected], [email protected] Seismology (S)

IstitutoNazionale di 2 - CNR, Istituto per l’Ambiente Marino e Costiero, Calata Porta di Massa - 80133 Naples, Italy; 3 - Università Roma 3, Largo San Leonardo Murialdo, 1 - 00156 Rome, Italy; 4 - Dipartimento di Scienze della Terra, Università degli Studi di Napoli Federico II, Largo San Marcellino, 10 - 80138 Naples, Italy Geofisica e Vulcanologia

CDP position (m) CROOKED LINE PLAN VIEW 300 400 500 600 700 800 900 1000 1100 1200 DATA ACQUISITION 1 Introduction. Seismicity and extensional basins in the Southern Apennines: a case study from the Vallo di Diano 0 Middle Late SALA4 HR profile Pleistocene 15°0’0"E 16°0’0"E 15°31’30"E 15°37’0"E 15°42’30"E Pleistocene ACQUISITION LINE fans 42°N PROCESSING LINE The stack section (Fig. 12 ) clearly fan Southern Adriatic Seismic Line MID PONT Apennines Sea 0.1 The axial portion of the Southern 1805 Fault VDFS RECEIVER POINT TheVallo di Diano (Fig. 2 ) is the largest extensional basin in the Southern Apennines. Its SHOT POINT VDFS (uncertain location) images the internal architecture of MID POINT AREA 40°N fault Tyrrhenian SALA4 profile was acquired with a Apennines thrust-belt (Fig. 1 ) is one of 1561 borehole (Karner et al., 1999) COMMON MID POINT BIN Basin REFLECTOR 99 northern sectorwas struck by a M 6.3 earthquake in 1561. The basin is bounded to the East Earthquake Alluvial fan (Middle alluvial fans (progradations foresets Pleistocene - Holocene) 40°30’0"N Fluvial andlacustrine deposits crooked geometry close to a quarry the most active seismic regions in the 38°N Arc 1731 Calabrian (Middle Pleistocene - Holocene outlined by black arrows) and their 0.2 1688 1456 for more than 35 km by NW-trending, SW-dipping normal and oblique-slip faults (Vallo di Polla Flysch (Miocene - Pliocene) Mediterranean area. Several Ionian Limestones,dolostones, exposing faulted Late Pleistocene fan

Basin 41°0’0"N 1702 36°N marls and cherls (Mesozoic - noticeable vertical displacement due 8°E 10°E 12°E 14°E 16°E 18°E Diano Fault System,VDFS ). Holocene surface faulting is reported for the northernmost Paleogene) earthquakes up to M7 struck the chain in 1456 1930 deposits (Figs. 10, 11 ). Middle 1732 Atena PERSPECTIVE VIEW toVDFS activity. Here, the VDFS fault TWT (s) the last two millennia. Present-day VDFS segments (Caggiano Fault , in: Galli et al., 2006; Fig. 2), while recent activity along the Lucana 0.3 Pleistocene 1851 The resulting stack section (Fig. 12 ) zone is about 500 m wide. 40°25 fan Mesozoic crustal seismicity is mainly related to a 41°0’0"N 1694 central and southern sets is uncertain. ’0"N depicts a complex array of faulted bedrock NE-directed extensional stress-regime. 1694 Commercial seismic lines image the large-scale structure of the basin documenting VDFS Sala alluvial fan generations covering the 0.4 Extension was accomodated by dip-slip activity up to the Middle Pleistocene (Amicucci et al., 2008). However, shallow imaging of the Consilina Fig. 10: Aerial view of SALA4 crooked line (X and Y coordinates in Fig. 11: Schematic 2D crooked-line profiling. Teggiano Mesozoic bedrock. m). The yellow dashed line is the acquired profile. The red line is the VDFS and oblique-slip faults which generated, VDFS is poor due unfavourable surface conditions and strong lateral heterogeneities along (a) plan view, (b) a segment of (a) and a cross- SW NE 40°20 processed profile. The pale blue area includes real midpoints. The line dipping reflector shown in a perspective 1561 since Lower-Middle Pleistocene, several 40°15’0"N ’0"N 0.5 Historical earthquake (Me > 6.3) the eastern basin border. yellow area is CMP bin area. view. The crooked profile is exaggerated for 1857 Fig. 12: SALA4 stack section with preliminary interpretation. intermountain basins. 23 November 1980, Ms 6.9 clarity (see Nedimovic and West, 2003). Irpinia Earthquake

Instrumental seismicty, 1981-2002 (earthquakes depth < 30 km) We present high-resolution seismic surveys targeting the basin structure 60 SW NE 525 Extensional fault active during Sala 3: 13x7 nodes

Fig. 1: Historical and instrumental seismicity of the Middle-Late Pleistocene 40°0’0"N 40 and the shallow structure of theVDFS . Our results yield clues of recent 515 Southern Apennines (Italy). The main inland Quaternary 1980 earthquake surface break SALA3 VHR profile 20 Southern Apennines buried

1000 V.E.=2x extensional faults are also shown. The yellow box encloses thrust-front 0 2,5 5 7,5 10 0 505 activity along the central segments of theVDFS , with significant Km the Vallo di Diano basin (Fig. 2). 0 1020304050 2000 Elevation (m)

40°0’0"N -20 Km The very-high resolution profile SALA3 was specifically 495 0 0 50 100 150 200 250 300 350 14°0’0"E 15°0’0"E 16°0’0"E implications for its seismogenetic potential. -40 00 The stack section, together with the Vp images, Fig. 2: Geological sketch of the Vallo di Diano 3 -0.075 designed to investigate surface flexures possibly Elev (m) basin. White box encloses the study area (Fig. 3). -60 strongly supports recent activity of theVDFS . Several 5000 relatable toVDFS recent activity (see also Figs. 4, 5) -80 ? ? fault splays displace both the bedrock and alluvial fans. -100 4000 0 Late Pleistocene -120 alluvial fans ? A normal-fault positioned at 280 m also cuts near- 2 - Purposes and Methods surface horizons. This fault well matches high-Vp steps 40 SW Sala 3: 27x11 nodes NE and a rapid thickening of near-surface soils illuminated Vp models show strong lateral changes (Fig. 13 ) 20 0.1 1000

TWT (s) by tomography. Diffractions at CDP positions 100 m Legend We acquired 3 high-resolution (HR) and 2 very high-resolution A HR Vibroseis was used to acquire all the profiles, with the exception of Sala3 (buffalo-gun). We around 250 and 280 m, which outline steps in the 0 -20 and 120 m indicate possible faulting of shallow layers, Sala1 line carbonate bedrock (Vp > 4000 m/s) and in the overlying

(VHR) profiles on the central segment of theVDFS (Fig. 3; Table combined reflection techniques with travel-time tomography, adapting thedense wide aperture crustal Elev (m) 2000 Sala2 line -40 alluvial fans (Vp=2000-3000 m/s). The steps suggest 3000 5000 0.2 as suggested by surface flexures. Sala3 line 4000 1), covered by Late Pleistocene - Holocene fan and lacustrine profiling (Ravaut et al., 2004) to shallow targets. Dense sources were recorded by a wide array of 168 -60 Sala4 line normal-faulting activity and well correspond upward to Mesozoic Padula line deposits. HR profiles targeted the shallowVDFS , VHR profiles geophones with a good compromise between its aperture (i.e. investigation depth) and the receiver soft and thick bodies (Vp < 1000 m/s) resembling -50 0 50 100 150 200 250 300 350 400 SW bedrcok NE surface warping and/or Distance (m) fault scarp crossed some intringuing flexures identified on Late Pleistocene interval (i.e. model sampling) (Fig. 6 and Table1 ). We thus collected both CMP reflection data and highly colluvial packages or entrapped sediments in the fault 0 100 200 300 quarry CDP position (m) Mesozoic-Paleogene fans (Figs. 4, 5 ). redundant first P-pulses. hangingwall. 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 limestones and dolostones Table 1 - Acquisition Geometry Vp (m/sec) Seg2 input Slope breccias and alluvial

40°22'30"N Sala 1 fan deposits Fig. 13. (top panel) Vp long-wavelength model; (bottom panel) Vp short- Fig. 14. (Top panel) High-precision topographic profile along SALA3 Seismic Shot Number of Receiver Receiver Overlapping Geometry (Lower-Middle Pleistocene) 525 Total Length (arrows indicate surface flexures; V.E.= 2x; see Fig. 5). (Bottom Legend Shots Spacing wavelength model. The yellow dashed line outlines resolution depth. Alluvial fan deposits SW NE Line Spacing spred size spreads FDSD Vibroseis correction 520 (Frequency Domain Sweep Deconvolution) (Middle-Late Pleistocene) topographic profile panel) stack-section (datum at 490 m a.s.l.).

.E.=3x Klauder Minimum Sala 2 surface warping '20"N 515 SALA1 1075 m 10 m 168 2 Sala 3 Alluvial fan deposits 100 5m Phase Conversion 40°22 (Late Pleistocene-Holocene) seismic line 510 Pre-Processing contour line SALA2 405 m 4m 98 2m 168 - Lacustrine deposits (elevation in m a.s.l.) 505 TV BP Filtering (Late Pleistocene Holocene) Sala3 (4) 168 500 SALA3 352 m 4m 90 2m - Spiking and/or surface consistent and/or predictive deconvolution Sala 4 495 SALA4 1315 m 10 m 101 5m 168 2 Statics 4 - Seismic imaging of the Vallo di Diano Basin: PADULA line Elevation (m) V 490 PADULA 3400 m 10 m 5m 168 5 TV BP Filtering 0 50 100 150 200 250 300 350 400 280 Options for Ground Roll and Air Wave Kill Trace 525 Removal CDP position (m) '10"N 540 SW NE Top Muting 40°22 Sala2 520 seismic line

.E.=3x 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500 2600 2700 2800 2900 3000 3100 3200 530 515 Fig. 15. (Top panel): stack-section of PADULA line; very Bottom Muting Offset analysis FK Filter Air Blast Attenuation 0 Sala3 (4) 520 510 Sala2 good-quality and significant signal was recorded down to 0.5 seismic line Sala3 (3) 505 We built reflectivity images by Seismographs sec TWT. A remarkable acquisition gap is due to crossing 510 CDP Sort First Arrivals 500 835 m Picking Vibration points highways. (Bottom panel): preliminary structural and 495 CDP-processing of reflection Velocity Analysis 500 0.1

Elevation (m) V 40°21'0"N Sala3 (3) stratigraphic intepretation.

'0"N 490 Geophones Tomography NMO Correction 40°22 0 50 100 150 200 250 300 350 400 data (Fig. 7 ). First-arrival Sala3 (2) layout 1 Sala3 (1) 490 525 520 SW NE F-K Pass over CDP travel-times were input to a Pre-Stack 480 .E.=3x 515 layout 2 Preliminary Stack 0.2 510 Our preliminary interpretation (Fig. 15 ) is Vallo di Diano Basin multi-scale, non-linear NO 505 OK? Sala3 (2) 0 100 200 300 400 500 600 700 800 900 1000 m Highway based on field and literature data, CDP position YES N 500

'50" tomography (Improta et al., 90 Residual Statics Gap 40°21 495 0.3

TWT (s) together with few chronostratigraphic 75 Velocity Analysis 475 0 200 Elevation (m) V m 490 2002) targeting the shallow 15°37'10"E 15°37'20"E 15°37'30"E 0 50 100 150 200 250 300 350 400 60 constraints (a 207 m deep well analyzed DMO Correction distance (m) VDFS with a gradually 45 Velocity Analysis by Karner et al., 1999). Padula Fig. 4: Details of some flexures Fig. 5: High-precision topographic profiles across the CDP fold 30 0.4 affecting a Late Pleistocene fan in flexures shown in Fig. 4. Red arrows indicate possible VDFS increasing spatial resolution. Eigen Filter 15 We relate the deepest sedimentary 0 1.000 Stack Section

the SALA3 survey site. surface expression. Post-Stack m Structural interpretation 0 bodies to a Pliocene (?) thrust-top wedge FX Deconvolution 0.5 Migration 40°19'30"N benefited from the integration (pre-datingVDFS generation) and Fig. 6: Pattern of “wide aperture” acquisition geometry and Migrated Section possibly Miocene flysch overlying folded 15°36'0"E 15°37'30"E 15°39'0"E of the different approaches. relative CDP folding (SALA1, SALA4 and PADULAl lines). Two Late Pleistocene - Holocene Holocene lacustrine 207-m deep borehole overlapping receiver spreads are illustrated. The maximum CDP alluvial fan deposits Fig. 7: Indicative processing flow and marsh deposits (projected, 500 m from the SE) Mesozoic cabonates. Fig. 3: Geological map of the Vallo di Diano sector targeted by fold is 90. (Karner et al., 1999) CDP position (m) the seismic surveys. Red lines with triangles indicate surface used for our data. Clear internal architecture of Pleistocene 200 300 400 500 600 700 800 900 1000 1100 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500 2600 2700 2800 2900 3000 3100 3200 flexures (possible splays of theVDSF ?). 0 stacked alluvial fan generations is imaged paleo- River Vallo di Diano depocenter Vallo di Diano Vallo di Diano on the eastern basin border (progradation alluvial fan sequence 600 kyr lacustrine sequence lacustrine and alluvial-fan Vallo di Diano (Middle Pleistocene) 0.1 fluvio-lacustrine sequence level (Late Pleistocene) sequence (Middle Pleistocene) outlined by black arrows). 3 - Seismic imaging of the VDFS along the eastern border of the Vallo di Diano (Middle Pleistocene) TheVDFS shows several synthetic- Vallo di Diano alluvial fan sequence Mt. Motola Vallo di Diano antithetic splays in a about 0.8 km wide (Lower-Middle Pleistocene) 0.2 transpressional fluvio-lacustrine sequence CDP position (m) (Lower-Middle Pleistocene) ? fault zone. It is moreover responsible for SALA1 HR profile faulted anticline the syn-sedimentary thickening of the 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 0.3 TWT (s) Lower-Middle Pleistocene fluvio- Alluvial fans ? ? ? thrust-top wedge ? Pliocene ? lacustrine and alluvial fan sequence filling Vp and reflectivity images for SALA1 profile (Figs. 8, 9 ) depict at least two main stacked alluvial fan generations that (Middle-Late Pleistocene) 0.4 Regional overthrust Miocene the basin. Possible splays reaching very sit atop the carbonate bedrock. TheVDFS shows several splays in a 600 m wide deformation zone. They displace Alburno-Cervati (Mt. Alburni thrust-sheet over flysch ? Unit Monti della Maddalena thrust-sheet) Monti della Maddalena shallow structural levels are found at CDP both Mesozoic bedrock and Late Pleistocene deposits, causing their noticeable back-tilting. 100 (Mesozoic-Paleogene) ? VDFS Unit positions 2900 m, documenting recent 0.5 (Mesozoic) NE Alluvial fans SW VDFS activity.

Sala 1: 12x7 nodes Sala1: 21x13 nodes 200 (Lower-Middle Pleistocene) 100 SW NE 100 SW NE 5 - Summary and Conclusions 300 50 50 Depth(m) 2000 2000 3000 References 0 0 1000 1000 3000 High-resolution seismic surveys in the Vallo di Diano basin provide new constraints on its structure and tectonic Karner D.D., Juvigne E., Brancaccio L., Cinque A., Russo Ermolli E., Santangelo N., 4000 400 Bernasconi S., Lirer L., 1999. A potential early middle Pleistocene tephrpstratotype fpr the

Elev (m)

Elev (m) -50 -50 Mediterranean basin: the Vallo di Diano, , Italy. Global and Planetary Change 21, 1-15 Mesozoic evolution: Improta L., Zollo A., Herrero A., Frattini M.R., Virieux J., Dell’Aversana P., 2002. Seismic imaging of complex structures by non-linear traveltime inversion of dense wide-angle data: -100 -100 bedrcok VDFS 500 - The Vallo di Diano basin origin pre-dates Pleistocene extension in the Southern Apennines belt axis (i.e. : the VDFS application to a thrust belt. Geophysical Journal International 151, 264-278 Nedimovic M.R., West G.F., 2003. Crooked-line 2D seismic reflection imaging in crystalline -100 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 -1000 100 200 300 400 500 600 700 800 900 1000 1100 1200 terrains: Part 1, data processing. Geophysics 68-1, 264-285 Distance (m) Distance (m) is superimposed on a pre-existing thrust-top basin) Ravaut C., Operto S., Improta L., Virieux J., Herrero A., Dell’Aversana P., 2004. Multiscale imaging of complex structures from multifold wide-apertire seismic data by frequency-domain full- 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 SW NE - The central segment ofVDFS consists of several shallow splays defining a 0.5-0.8 km wide fault zone waveform tomography. Geophysical Journal International 159-3, 1032-1056 doi:10.1111/j.1365- Vp (m/sec) 246X.2004.02442.x - TheVDFS displaces Late Pleistocene alluvial fans, but recent sediments seal most of fault splays Galli P., Bosi V., Piscitelli S., Giocoli A., Scionti V., 2006. Late Holocene earthquakes in Southern Fig. 8a: SALA1 Vp long-wavelength model. The yellow line outlines resolution Fig. 8b: SALA1 Vp short-wavelength model. The yellow line outlines Fig. 9: SALA1 depth-converted, migrated stack-section with simplified structural and stratigraphic interpretation. Apennine; paleoseismology of the Caggiano Fault. Geologische Rundschau 95-5, 855-870 depth (estimated by checkerboard tests). resolution depth. Amicucci L., Barchi M.R., Montone P., Rubiliani N., 2008. The Vallo di Diano and - The VHR profile SALA3 shows clues to very recent (Holocene) surface faulting extensional basins in the southern Apennines (Italy): a simple model for a complex setting. Terra Nova, in press - This study proves the recent activity of the central segment of the VDFS