GNGTS 2018 - 37° Convegno Nazionale

GNGTS 2018 S essione 1.2 205 Catalano S., Romagnoli G. and Tortorici G.; 2010: Kinematics and dynamics of the Late Quaternari rift-flank deformation in the Hyblean Plateau (SE Sicily). Tectonophysics 486, pp. 1-14. doi:10.1016/j.tecto.2010.01.013. Chiarabba C. and Palano M.; 2017: Progressive migration of slab break-off along the Tyrrhenian plate boundary: Constraints for the present day kinematics. J. of Geodyn., 105, pp 51-61. Bonforte A., Catalano S., Maniscalco R., Pavano F., Romagnoli G., Sturiale G., and Tortorici G.; 2015: Geological and geodetic constraints on the active deformation along the northern margin of the Hyblean Plateau (SE Sicily). Tectonophysics 640-641; pp. 80-89. Ghisetti F. and Vezzani L.; 1980: The structural features of the Hyblean Plateau and the Mount Judica area (South- Eastern Sicily): a microtectonic contribution to the deformational history of the Calabrian arc. Bollettino della Società Geologica Italiana, 99, pp. 55–102. Musumeci C., Patanè D., Scarfì L., and Gresta S.; 2005: Stress direction and shear-wave anisotropy: Observations from Local earthquakes in southeastern Sicily, Italy. Bull. Seismol. Soc. Am., 95 (4), pp. 1359-1374. Polonia A., Torelli L., Mussoni P., Gasperini L., Artoni A., and Klaeschen D.; 2011: The Calabrian arc subduction complex in the Ionian Sea: regional architecture, active deformation and seismic hazard. Tectonics 30, TC5018 doi: 10.1029/2010TC002821. Postpitschl D.; 1985: Catalogo dei terremoti italiani dall’anno 1000 al 1980. CNR, P.F. Geodinamica, Graficoop Bologna, 239 pp. Vollrath A., Zucca F., Bekaert D., Bonforte A., Guglielmino F., Hooper A.J., and Stramondo S.; 2017: Decomposing DInSAR Time-Series into 3-D in combination with GPS in the case of low strain rates: An application to the Hyblean Plateau, Sicily, Italy. Remote Sensing, 9, pp. 1-22. doi: 10.3390/rs9010033. CONVERGENCE RATE VERSUS BRITTLE-DUCTILE TRANSITION DEPTH IN COMPRESSIONAL SETTINGS: CONSIDERATIONS ON SEISMOGENIC VOLUME AND POTENTIAL EARTHQUAKE MAGNITUDE P. Petricca 1 , E. Carminati 1 , C. Doglioni 1,2 , F. Riguzzi 2 1 Sapienza Università di Roma, Rome, Italy 2 Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy Earthquakes magnitude increases with the rock volume involved in the coseismic stage (Bath and Duda, 1964; Doglioni et al. , 2015a; Petricca et al. , 2015) in turn constrained by the fault length (e.g., Leonard, 2010) and the depth of the brittle-ductile transition (BDT). The distribution of earthquake hypocenters gives a first approximation of the seismogenic thickness, and hence of the maximum depth of faulting (Chiarabba and De Gori, 2016). For earthquakes with magnitude Mw>5 worldwide, earthquakes foci deepen where the largest events have been recorded (Mw>8.5), ranging in depth from 25 to 50 km and almost coinciding with convergent plate boundaries regions (e.g., Sumatra, Japan, Chile). Shallower hypocentral depths (25 km) typify divergent and strike-slip margins where rarely Mw=8. Largest volumes are mobilized in convergent tectonic settings as thrust faults display the higher ratio between fault length and hypocenter depth (up to more than 25) with respect to strike-slip and normal faults (around 10 and 3 respectively) (Doglioni et al. , 2015a). Furthermore, released seismic energy scales with convergence rate (Bird et al. , 2009; Ide, 2013; Ruff and Kanamori, 1983). While rupture-scaling relationships are routinely used in seismic hazard studies, (non) linear relations between relative plate velocity and seismicity rate or moment rate or maximum possible magnitude are harshly debated. Comparing convergence rates from GPS data with seismogenic depths extrapolated from available regional studies we found that the faster the convergence, the thicker this seismogenic layer (Fig. 1). For convergent plate margins, minimum seismogenic layer thicknesses (10–15 km) occur in slowly (0–2 cm/ yr) convergent realms (Calabrian Arc, Apennines, Aegean and Zagros). Such thickness values increase to around 20 km in intermediate (4–6 cm/yr, i.e. India) convergent settings. The