GNGTS 2015 - Atti del 34° Convegno Nazionale

GNGTS 2015 S essione 1.1 57 Singh, D. D., and H. K. Gupta (1980), Source dynamics of two great earthquakes of the Indian subcontinent; the Bihar–Nepal earthquake of January 15, 1934 and the Quetta earthquake of May 30, 1935, Bull. Seismol. Soc. Am. 70 (3), 757–773. Sirovich, L., F. Pettenati, F. Cavallini, and M. Bobbio (2002), Natural-neighbor isoseismals, Bull. Seismol. Soc. Am., 92, 1933–1940. Sirovich, L., and F. Pettenati (2004), Source inversion of intensity patterns of earthquakes: Adestructive shock in 1936 in northern Italy, J. Geophys. Res., 109, B10309, doi:10.1029/2003JB002919. Stephenson, B. J., M. P. Searle1, D. J. Waters1, and D. C. Rex 158 (2001), Structure of the Main Central Thrust zone and extrusion of the High Himalayan deep crustal wedge, Kishtwar–Zanskar Himalaya, Journal of the Geological Society, 158, 637–652. SUBMARINE EARTHQUAKE GEOLOGY AS A TOOL FOR SEISMIC HAZARD ASSESSMENT IN THE CALABRIAN ARC A. Polonia 1 , S. Romano 1 , L. Gasperini 1 , S.C. Vaiani 2 , G. Gasparotto 2 , E. Colizza 3 , L. Torelli 4 1 Institute of Marine Sciences (ISMAR-CNR), Bologna, Italy 2 Dipartimento di Scienze Biologiche, Geologiche e Ambientali, University of Bologna, Italy 3 Dip. di Matematica e Geoscienze, Universita’ degli Studi di Trieste, Italy 4 Dipartimento di Fisica e Scienze della Terra “Macedonio Melloni”, University of Parma, Italy Introduction. Paleoseismology is the investigation of individual earthquakes from their geological signatures such as those produced directly along the rupture plane, and those produced indirectly (landslides and, in general, mass wasting processes in the vicinity of faults). If datable material is recovered from stratigraphic horizons that experienced successive ruptures, slip rate and time separation between large earthquakes can be reconstructed. Earthquake geology has been widely applied to major continental faults in the Calabrian Arc over the past decades (Valensise and Pantosti, 1982; Galli et al. , 2003, 2008, 2015).While paleoseismology has become a primary tool for seismic hazard evaluation on land, only few paleoseismological studies have been attempted on submarine fault systems, mainly because of the limited resolution of the available geophysical techniques used at sea. Rapid developments in imaging and sampling techniques have now made such studies possible. Submarine paleoseismological studies have the following advantages compared to those undertaken on land: (i) marine sedimentation is generally more continuous in time and space, allowing for regional stratigraphic correlations; (ii) offshore data can be acquired more quickly. Innovative techniques have been developed which makes submarine paleoseismology feasible (Polonia et al. , 2012, 2013a, 2013b, 2015). They include (i) high-resolution morphobathymetric images of the seafloor, (ii) 3-D and pseudo- 3D high resolution seismic reflection imaging, and (iii) detailed stratigraphic reconstruction of the sedimentary record. Although submarine geophysical data have lower resolution than classic paleoseismological trenching, they provide complete spatial coverage of fault structures, both horizontally and vertically. This will allow accurate long time-scale, high-resolution reconstruction of fault-zone evolution. During the last years, we applied such methodology to the submerged Calabrian Arc and surrounding areas of the central Mediterranean Sea during a number of oceanographic expeditions with R/V CNR Urania (2008, 2012, 2013, 2014, 2015). Interplay between seismic shaking, tsunamis and mass flows. Submarine geohazards, such as major earthquakes, tsunamis, volcanic eruptions, volcanic flank collapse and submarine landslides, are isolated and exceptional events capable of producing large-volume turbidites that result from catastrophic submarine slope failures and the associated downslope mass transport of enormous quantities of sediment from continental shelves and slopes to the deep sea. In this study, we analyse the interplay between tectonics and sedimentation along the Africa/Eurasian plate boundary in the Ionian Sea through an integrated approach involving