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Seismic Site Effects in the Faulted Area (): An Explanation Attempt

M. I. Rainone Geotechnologies for the Environment and the Territory “G. d’Annunzio” University of Chieti-Pescara, Italy

P. Torrese University of Pavia, Italy

P. Signanini Geotechnologies for the Environment and the Territory “G. d’Annunzio” University of Chieti-Pescara, Italy

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Recommended Citation Rainone, M. I.; Torrese, P.; and Signanini, P., "Seismic Site Effects in the Faulted Piancastagnaio Area (Italy): An Explanation Attempt" (2008). International Conference on Case Histories in Geotechnical Engineering. 27. https://scholarsmine.mst.edu/icchge/6icchge/session03/27

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SEISMIC SITE EFFECTS IN THE FAULTED PIANCASTAGNAIO AREA (ITALY): AN EXPLANATION ATTEMPT

M.L. Rainone P. Torrese P. Signanini Di.G.A.T. (Department of Department of Earth Sciences Di.G.A.T. (Department of Geotechnologies for the Environment University of Geotechnologies for the Environment and the Territory Pavia, Italy. and the Territory “G. d’Annunzio” University of “G. d’Annunzio” University of Chieti-Pescara, Italy. Chieti-Pescara, Italy.

ABSTRACT

Analysis of seismic site effects is still an open issue within projects that deal with the reduction of seismic risk. In the absence of surface and borehole arrays measurements, the main methodological approach consists of the individuation and the consequent appraisal of the surface effects in presence of “an expected” earthquake, through integrated geological, geomorphological, geological- technical, geophysical multidisciplinary surveys and by the use of numerical modelling. In historically densely populated urban areas, it is possible to verify if the calculated accelerations can be, at least qualitatively, correlated to the level of damage to buildings. However, there are frequent cases in which meaningful incongruences between modelling results and macroseismic effects are found. In particular, this note shows the case of Piancastagnaio (Central Italy), a small town in which an earthquake occurred in 2000 with a local magnitude ML = 3.6. In some buildings, constructed in the 1920's with earthquake-proof criteria for the times, this earthquake caused cracks justified only with intensities of VIII-IX degree of the EMS scale. The results of the analysis, carried out in compliance of the new Italian (D.M. dated 14.09.05, O.P.C.M. 3274 dated 20.03.03 and followings) and European (Eurocode8 dated 2003) seismic code and which classify the subsoil on the basis of the Vs30 values, do not justify such strong anomalous amplifications. With this work, the authors attempt an explanation of this kind of phenomenon and identify failure mechanisms as the cause of the identified local effects.

INTRODUCTION

Faults and surficial fractures are crucial elements that must be considered within the assessment and analysis of risk associated with seismic events and the study of local seismic response. Faults and seismic fractures (active, seismogenetic, etc.) or any other surficial discontinuity, that can be generically identified as faultings, must be considered under a multidisciplinary approach (sismology, structural geology, technical geology, etc). However, this approach must not disregard the complexities of local seismic response.

Geological faulting is neither rare nor isolated. There are several events that can be recalled in Italy, relating to both recent (Friuli 1975, Irpinia 1978, Umbria-Marche 1997) and historical (Messina 1908, Senigallia 1930) earthquakes. Several authors have dealt with these phenomenons. Amongst them, Keefer & Tannaci (1981) analysed 47 seismic events recorded between 1811 and 1980, of magnitude between 5.2

Fig. 1. Location and geological map of the studied area.

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and 8.6. The observations of these authors focused on the fact contact between lithologies of different physical and that faulting phenomenons are more relevant rather than their mechanical behaviour, different degrees of compaction within induced effects like landslides, soil liquefaction, etc. Faulting, granular deposits, etc. This concept of the phenomenon is as intended by the authors, is an effect that is visibile at the significantly broader than the one to which the various task surface following a seismic event. forces dealing with the new Italian (Norme tecniche per le costruzioni D.M. 14 settembre 2005) and European (Eurocode 8 dated 2003) regulations are oriented towards. There is abundant literature to this respect (Evison, 1963; Davis and West, 1973; King and Vita Finzi, 1981; Dramis et al., 1982; Slemmons and de Polo, 1986; Blumetti et alii, 1993; Tibaldi, 1998).

Fig. 2. Damaged building located at podere Sugherelle in Piancastagnaio (SI), after Amiata earthquake in 2000; “x” lesions (pointed out in red lines) implies VIII-IX degree of MCS scale.

Fig. 4. U/D, N/S and E/W components of a recorded waveform and physical ductility spectrum (PDS) of u/d component for a local hydraulic-type earthquake (by Borgia et al., 2002).

THE AREA OF PIANCASTAGNAIO AND THE 2000 EARTHQUAKE Fig. 3. U/D, N/S and E/W components of a recorded waveform and physical ductility spectrum (PDS) of u/d component for a The town of Piancastagnaio (Central Italy, Region, local tectonic-type earthquake (by Borgia et al., 2002). Province of ) is located near the geothermal area of the Mount Amiata region (Fig. 1). The area has experienced some Different causes of different genesis can converge within this earthquakes during the the period from 1997 to 2000. phenomenon: a buried fault, whether active or not active, The most severe damages occurred during the seismic event of whether a principal or derived fault, a simple displacement 1 April 2000, with epicentre located in the area immediately to within the solid bedrock that causes an effect at the surface, the south of Piancastagnaio. Although low energy was

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released during the earthquake (Md=3.8, Ml=3.6), a series of Boccaletti et al., 1987; Calamai et al., 1970; Decandia et al., buildings that were built in the 1920's according to anti- 1998; Liotta, 1995). The area lies in a tectonically depressed seismic concepts, experienced severe damages (Fig. 2), with area bounded by normal faults with a listric geometry macro seismic intensity of VIII-IX degree of EMS scale). (Miocene-Pliocene basin of ). The depressed area lies between the Poggio Zoccolino-Mount Amiata-Mount Civitella dorsal to the west and the Mount dorsal to the east. Geologically, the area lies within the the Mount Amiata region that has experienced volcanic activities. The basal elements of the volcanic series, which are characterised by ignimbritic and trachyte-dacitic deposits of the Pleistocene period, can be observed in the north west sector of Fig. 1.

Sandy clayey deposits and clayey sandy deposits from the lower Pliocene are found in the high standing areas and hills that experienced significant damages from the earthquake. Fluvial lacustrine deposits, occasionally thicker than ten meters, are found in the low standing areas near the streams. A correlation between the spatial distribution of the damages and the geological context of the area is difficult to establish. Therefore, the geological context on its own is not sufficient to explain this anomalous distribution.

There are some geothermal stations in the area that, like all the geothermal stations of the Amiata area, separate vapour from the fluid-vapour flow that is produced from the wells.

THE SEISMICITY OF THE AMIATA AREA

Historical records for seismicity in the Amiata region show variable intensities that range from 5.5 to 9 within the MCS scale. Depths of hypocentres are shallow and within 4 to 6 km. The spatial distribution of epicentres is aligned in a north west to south east direction and outlines the Radicofani graben which is the most significant structural element of the area. Therefore, the seismicity of the area is characterised by both tectonic related activity and that related to volcanic activity of Mount Amiata. Seismic monitoring undertaken by E.D.R.A. S.r.l. (European Drilling Rig Alliance, Borgia et al., 2000, 2002) between 1999 and 2002 has shown that the seismic activity of the area is frequent and of low intensity. Borgia et al. have defined two typologies of earthquakes: • local tectonics (Fig. 3) characterised by low energy (<2 M), modest duration (< 20 sec), high spectral frequency (10 to Fig. 5. SUGST2 refraction seismic section carried out at 20 Hz, recorded at less than 30 Km from the epicentre), podere Sugherelle. mostly arrivals of P waves; • hydraulic fracturing (Fig. 4) characterised by longer Some colonic houses experienced severe damages and in most duration (sometimes > 40 sec), an initial phase of 3 to 5 cases they were structural damages. Other buildings, located at seconds and high frequency (15 to 20 Hz) followed by a a few meters from the previous, experienced minor damages. low frequency phase (1 to 3 Hz), no shear waves; these The spatial distribution of the damages can be defined as earthquakes are probably generated by a water filled “leopard spotted”. The anomalous distribution of the damages fracture where the initial breaking generates the high could not be correlated to the different vulnerability of the frequency phase of the wave and the following resonance buildings. It did however suggest that there could have been a of the fracture produces the monochromatic tail of the wave strong probability of seismic amplification connected to local (Aki et al. 1977, Chouet, 1986, Kumagai & Chouet, 2000, effects. 2001); this typology of earthquake has been identified in several volcanic areas rich in geothermal fluids. The geological and structural context of the area has been described by several authors (A.A.V.V., 1977; AA.VV. 1991; Abbate et al. 1982; Anselmi, 2000; Bertini et al., 1991;

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Fig. 7. SUGST2 refraction seismic section with P and SH waves obtained by tomographic inversion.

ANALYSIS OF THE LOCAL SEISMIC RESPONSE

First phase of investigations and analysis

Detailed technical geological and geophysical investigations were undertaken (21 refraction lines in P and SH waves, Figg. 5, 8). These investigations enabled the reconstruction of the principal characteristics of the subsurface, both in terms of elastic-dynamic parameters and in terms of geometries. The Fig. 6. Input motion used in 1D modeling and estimated subsurface was classified according to the Vs30 value criterion response spectra compared with B category response spectra prescribed by Italian (D.M. dated 14.09.05; O.P.C.M. 3274 of the normative. dated 20.03.03 and updates) and European (Eurocode8 dated 2003) regulations. Numerical modelling was undertaken using The origin of seismicity within the Mount Amiata region can a 1D equivalent linear analysis (ProShake code by EduPro thus be connected to both a tectonic component associated Civil System Inc, Idriss & Sun, 1992; Schnabel et al., 1972). with the seismogenetic Graben of Radicofani and a component Figure 5 shows the SUGST2 refraction seismic section with related to the geothermal fields. SH waves that was acquired at Podere Sugherelle (one of the most badly hit areas during the 2000 earthquake). The results It is worth noting that there is a strong correlation between the of the one-dimensional modelling (SUGST2-1, SUGST2-2, damaged areas of the 2000 earthquake and those of the more SUGST2-3) relative to a extremely damaged building, intense 1919 earthquake (equivalent magnitude of 5.3). founded on category B (D.M. dated 14.09.05) soils, is also shown. A real horizontal accelerogram with a spectral content ranging from 8 to 12 Hz (Fig. 6) was used as input motion due to the absence of local recordings. This accelerogram, which was scaled for a PGA=0.14g, is compatibile with recordings of local earthquakes and was provided by the National Seismic Service (O.P.C.M. 3274) for the town of Piancastagnaio. The models show spectral responses with maximum accelerations that are almost double the input values (Fig. 6). They are characterised by low amplifications which are lower than the values prescribed by regulations. This does not apply to the

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lower periods (frequency equal to 12.5Hz) which are of no interest under an engineering point of view.

Fig. 9. Location of lineations by photo-interpretation.

Fig. 8. Location of refraction (P and SH waves) and reflection Fig. 10. Ln1 reflection seismic section with SH waves carried (SH waves) seismic lines, 1D modeling sites and 2D modeling out at podere Sugherelle (fractures in red line). section carried out at podere Sugherelle. Discontinuities located by photo-geological and seismic analysis are pointed Distinct groupings of circular fractures and two separate linear out in red and orange, respectively. trends of fractures (one with a north south direction and the other with a north east to south west direction) are observed thus producing clusters with high density of fractures. This The scarse relationship between the result of the modelling phenomenon appears to be more pronounced in the area of and the macro seismic effects was apparent, especially podere Sugherelle, which is the area that experienced major considering that a geomechanical investigation near the damages (Fig. 9). building showed the presence of a single clayey marly lithotype underlying a one meter thick layer of eluvial- High resolution reflection seismic using SH waves was colluvial deposits. accomplished in order to confirm the presence of the above

faultings (Fig. 8). A reflection section undertaken at podere

Sugherelle, in an area subject to urbanisation, is shown in Fig. Second phase of investigations and analysis 10: interruption of continuity of the reflectors can be observed (already noticed from aerial photo surveys and refraction Tomography techniques (Fig. 7) were used to reinterpret the seismics Fig. 8). The major interruptions are observed at seismic sections and thus allow an understanding of the depths of 8 m and 58 m below the surface and also produce principal causes of these anomalous amplifications. This disconnections of the upper reflectors. It was thus concluded inversion method was particularly efficient due to the local that the local effects were caused by faulting for this specific geological conditions (clayey marls that are less weathered setting outlined at Podere Sugherelle and for other similar with depth) that caused a progressive increase in the seismic settings in the Piancastagnaio area. velocity thus producing curved dromochrones. A three layer model, obtained with the classic refraction inversion method, Based on this hypothesis and on the newly acquired was used as an input model for the tomographical processing. knowledge, an attempt to assess if a faulting system like the It is interesting to note that the resulting sections (Fig. 7, 8) previously outlined setting could explain the observed identify the presence of discontinuities that appear to correlate anomalous macro seismic effects. A 2D finite element with those identified from aerophotogrammetry. Several numerical model using an equivalent linear analysis (Quake/W lineament systems were identified from interpretation of the code by GEO-SLOPE International Ltd.) was constructed for aerial photos acquired in 1993 and 1954 and with the assessment. Modulus and damping curves for the different geomorphological surveys (Fig. 9). A map illustrating the soils were obtained by geotechnical tests carried out on soil surficial lineaments was constructed from these observations samples. Different couplings between the faulted blocks and and was used to verify if the damages could be correlated to seismic input conditions were used. Two extreme case models the lineaments (Fig. 3).

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were built due to the poor understanding of the existing • model 1 or “connected” model: a continuous section physical-mechanical parameters between the blocks: where the fractures are represented as vertical contacts between different lithologies of different thicknesses. • model 2 or “disconnected” model: the discontinuities are represented by a missing bond coupling so that an infinitesimal space was left between the two sides of the fractures.

Fig. 11. Section with blocks used for 2D modeling.

Fig. 12. Accelerograms, displacements and response spectra obtained with 2D modeling of fault 1 with PGA=0.014, model 1.

Geometry of 2D models is shown in Fig. 11 in which are The typical wave form used for the 1D models was also used simulated the worst case scenario where the coupling between for the 2D models as an input motion. Scalings with a the blocks is zero and the best case scenario where the PGA=0.14 g and a PGA=0.05 g were used. The later value coupling of the model is equal to one. was used in consideration of the fact that it adapts to a 3.7

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magnitude of the Richter scale which was recorded during the The results of modelling the immediate areas in the vicinity of earthquake of the 1 April 2000. This PGA value was based on fault 1 are shown in Fig. 12 to 14. The analysis of these figure data correlations of intensity, soil displacement, acceleration shows the following: and period of the seismic waves, obtained from the Observatory of Experimental Physics of Trieste (Rebez & Stucchi, 1996).

Fig. 13. Accelerograms, displacements and response spectra obtained with 2D modeling of fault 1 with PGA=0.014, model 2.

• model 1 with PGA=0.14 g (connected) shows elevated • model 2 with PGA=0.14 g (disconnected) shows elevated amplifications when compared to the input (3.5 for the accelerations when compared to the input (6 for the acceleration, 7.5 for the result spectrums) while both the acceleration, 5-10 for the result spectrums) and high maximum and differential displacement at the edge of displacements, especially differential displacements greater fracture 1 are low and in the order of millimeters (Fig. 12, than 2 cm at the boundary of fracture 1 (Fig. 13, Tab. 1); Tab. 1); • model 2 with PGA=0.05 g (disconnected) shows high when compared to inputs (Fig. 14, Tab. 1). accelerations (6 for the acceleration, 8-12 for the result The above observations have clearly revealed that the faulting spectrums), low maximum displacements and medium has played an important role in causing local amplification. differential displacements at the boundary of fracture 1 The maximum accelerations of the calculated response

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spectrums for the different models are significantly higher faulting was the main cause of the anomalous amplification than those prescribed by regulations for a class B soil effects recorded in the Piancastagnaio area. (between 2 and 5 times). In this sense, the presence of surficial

Fig. 14. Accelerograms, displacements and response spectra obtained with 2D modeling of fault 1 with PGA=0.05, model 2.

Tab. 1. Accelerations, response spectra and displacements obtained with 2D modeling of fault 1.

Numerical Modeling 1D 2D 2D 2D Blocks model Blocks model Blocks model Model type - Coupling = 1 Coupling = 0 Coupling = 0 (Pga Input = 0.14g) (Pga Input = 0.14g) (Pga Input = 0.05g) 3.5 times input 6 times input 6 times inpt Accelerations 2 times input (both sx and dx (both sx and dx (both sx and dx of the fault) of the fault) of the fault) 7 times input Sx= 10 times input Sx= 12 times input Response Spectra 2 times input (both sx and dx Dx= 5 times input Dx= 8 times input of the fault) Max = 6mm Max = 1.4 cm Max = 6mm Horizontal Displacements Max 2 cm Diff = <1mm Diff = 2.3 cm Diff = 1cm Max = 3mm Max = 8mm Max = 2mm Vertical Displacements - Diff = 1mm Diff = 1cm Diff = 4mm

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CONCLUSIONS Abbate et al. [1982], “Carta strutturale dell’Appennino settentrionale”, C.N.R. Prog. Fin. Geod. Pubb., 249. The case study of the Piancastagnaio area is presented in this work. The objective was to understand how a low energy Anselmi B. [2000], “Monte Labbro e alta valle dell’Albegna, earthquake caused damages that are compatible with macro tutela e gestione”, mountain community, “life seismic intensities that are normally encountered with high nature” project. magnitude earthquakes. During the first phase of the studies, monodimensional models based on the geometrical AA.VV. [1977], “La Toscana meridionale“, Rend. Soc. It. characterisation and the dynamic parameterisation of the Min. Petr., 27, Vol. Spec. subsurface had estimated amplifications that were significantly lower than those prescribed by regulations. AA.VV. [1991], “Studi preliminari all’acquisizione dati del Therefore, in the absence of significant bidimensional effects, profilo CROP03 Punta Ala - Gabicce“, St. Geol. Camerti., the estimated stratigraphical amplification showed a scarse 1991/1, Vol. Spec. relationship with the observed macro seismic effects. Different systems of fractures, confirmed by HR reflection seismics, Bertini A., Costantini A., Cameli G.M., Di Filippo M., were identified both at the surface and at depth only during the Decandia F.A., Elter M.F., Lazzarotto A., Liotta D., Pandeli second phase of study. This was achieved by an integrated E., Sandrelli F. and Toro B. [1991], “Struttura geologica dai analysis of refraction seismic investigations processed with Monti Campiglia a (Toscana Meridionale): inversion tomography and coupled with aerophotogrammetry. stato delle conoscenze e problematiche“, St. Geol. Camerti, Based on the new findings, it was concluded with the aid of Vol. Spec., 1991/1 Crop 03, 155-178. 2D modelling that surficial faulting was the primary cause of the anomalous amplifications noticed in the Piancastignaio Blumetti A.M., Dramis F. and Michetti A.M. [1993], “Fault- area. The spectral response of two extreme case models, based generated mountain fronts in Central Apennines (Central on a different coupling of contact between the blocks, proved Italy); geomorphological features and seismotectonic that the maximum accelerations were higher that those implications“, Earth Surf. Processes Landf., 18, 203-223. accepted by current regulations. Boccaletti M., Decandia F.A., Gasperi G., Gelmini R., On the understanding that the problematics that are inherent to Lazzarotto A. and Zanzucchi G. [1987], “Note illustrative alla the presence of faults or phenomenons generically known as carta strutturale dell’Appennino Settentrionale”, Prog. Fin. faultings are complex and articulated, it brings out the fact that Geod. Sottoprg. 5, Mod. Str. Gr. App. Sett.. Pubb. N. 429, the above issues are currently unresolved by present 1982, Tipografia Senese, 1987. regulations. This is due to poorly defined criteria, which appear to be vague and are not sufficiently incisive when Borgia A., Ripepe M., Della Schiava M. [2000], “Indagine compared to the requirements of effective and appropriate sismica dell’area di Piancastagnaio e . engineering techniques. Relazione sull’installazione della rete sismica locale”, Technical report E.D.R.A. S.r.l. (European Drilling Rig Alliance). ACKNOWLEDGEMENTS Borgia A., Ulivieri G. and Marchetti E. [2002], “La sismicità The authors would like to thank: architect Maurizio Ferrini, del Monte Amiata nei comuni di Abbadia San Salvatore e Director of Seismic Service of Tuscany Region for allowing Piancastagnaio dal maggio 2000 al giugno 2001”, Technical the publication of the work; geologist Raffaele Madonna, report E.D.R.A. S.r.l. (European Drilling Rig Alliance). geologist Fabio Pizzica and geologist Francesca De Finis for the precious contributions during the data acquisition, Calamai A., Castaldi R., Squarci P. and Taffi L. [1970], collection and homogenisation respectively; engineer “Geology, Geophysics and Hydrogeology of the Monte Giovanna Vessia for the precious contribution during the fine Amiata Region”, Geothermics, Special Issue, 1970. tuning of the 2D models; geologist Antonio Gennarini and geologist Carlo Caso for the precious collaboration. CEN (European Committee for Standardization) [2003], “Eurocode 8: Design of structures for earthquake resistance.” Chouet B. [1986]. “Dynamics of a fluid-driven crack in three dimensions by the finite difference method”, J. Geophys. Res., REFERENCES 91, 13967-13992.

Aki K., Fehler M. and Das S. [1977], “Source mechanism of Davis L.L. and West L.R. [1973], “Observed effects of volcanic tremors: fluid driven crack models and their topography on ground motion”, Bull. Seismol. Soc. Am., 63 application to the 1963 Kilauea eruption”, J. Volcanol. (1), 283–298. Geotherm. Res. 2, pp. 259–287.

Paper No. 3.13 9

Decandia F.A., Lazzarotto A., Liotta D., Cernobori L. and Schnabel P.B., Lysmer J., Seed H.B. [1972], SHAKE a Nicolich R. [1998], “The CROP03 traverse: insights on post- computer program for earthquake response analysis of collisional evolution of the Northern Apennines”, Mem. Soc. horizontally layered sites, User’s Manual, Earthquake Geol. It., 52, 427-439. Engineering Research Center, University of California, Berkeley. Dramis F., Genevois R., Prestininzi A., Lombardi S. and Cognini L. [1982], “Surface fractures connected with the Slemmons D.B. and De Polo C.M. [1986], “Evaluation of Southern Italy eartquake (November 1980) – Distribution and active faulting and related hazard”, In: Wallace R.E. (Ed.), geomorphological implications”, Proceed. IV Congr. IAEG, Active Tectonics, Studies in Geophysics. National Academy New Delhi 1982, 8, 55-66. Press, Washington DC, pp. 45-62.

Evison F.F. [1963], “Earthquakes and faults”, Bull. Seism. Tibaldi A. [1998], "Effects of topography on surface fault Soc. Am., 53 (5), 873-891. geometry and kinematics: examples from the Alps, Italy and Tien Shan, Kazakstan, " Geomorphology, 24, 225-24. Idriss I.M. & Sun J.I. [1992], “SHAKE 91: A computer program for conducting equivalent linear seismic response analyses of horizontally layered soil deposits”, User’s Guide, University of California, Davis, California, 13 pp.

Keefer D.K. and Tannaci N.E. [1981], “Bibliography on landslides, soil liquefaction and related ground failures in selected historic earthquakes”, U.S. Geological Survey Open- File Report, 81-572.

King G.C.P. and Vita Finzi C. [1981], “Active folding in the Algerian earthquake of 10 October 1980”, Nature, 292, 22-26.

Kumagai H. and Chouet B. [2000], “Acoustic properties of a crack containing magmatic or hydrothermal fluids”, J. of Geophys. Res., 105(B11), doi: 10.1029/2000JB900273. issn: 0148-0227.

Kumagai H. and Chouet B. [2001], “The dependence of acoustic properties of a crack on the resonance mode and geometry”, Geophys. Res. Letts., 28(17), doi: 10.1029/2001GL013025. issn: 0094-8276.

Ministero Infrastrutture e Trasporti. D.M. 14 settembre 2005, “Norme tecniche per le costruzioni”, Pubblicato sulla G.U. n. 222 del 23 settembre 2005 S.O. n. 159.

Liotta D. [1995], “Analisi del settore centro-meridionale del bacino Pliocenico di Radicofani”, Boll. Soc. Geol. It., 115, 115-143.

Presidente del Consiglio dei Ministri. Ordinanza 3274 del 2003, “Primi elementi in materia di criteri generali per la classificazione sismica del territorio nazionale e di normative tecniche per le costruzioni in zona sismica”, Pubblicata nel Supplemento Ordinario n. 72 della G.U. n. 105 del 8.05.2003.

Rebez A. & Stucchi M. [1996], “La determinazione della Ms a partire da dati macrosismici per i terremoti compresi nei cataloghi NT, GNDT”, Rapporto interno, Trieste-Milano, 48pp.

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