GNGTS 2018 - 37° Convegno Nazionale

24 GNGTS 2018 S essione 1.1 Similarly, caution is needed in the use of AD and MD, for Seismic hazard analysis, when obtained indirectly from other parameters (fault length, expected magnitude). Finally the use of displacement values and slip rates for calculating recurrence times of large earthquakes have to be carefully evaluated: in fact, using displacement values measured on a section of the fault where D~AD and slip rate values obtained in a section close to MD, lead to underestimate the recurrence time and vice versa. In other word, when the aforementioned coseismic parameters are to be used for these purposes it is necessary, as much as possible, to determine them at the same point of the fault. References Boncio, P. Testa, A., Di Donato, M. Mataloni, G. Palumbo D. and Le Donne L. (2018). Parameters of the 2016 central Italy earthquake surface faulting (M 6.5, normal fault) and comparison with global data. Abstract proceedings of the the PATA Days 2018 - Greece, 24-29 June 2018. Wells, D., L., K. J. Coppersmith, (1994), New Empirical Relationships among Magnitude, Rupture Length, Rupture Width, Rupture Area, and Surface Displacement, Bullettin of the Seismological Society of America, Vol.84, No. 4, pp. 974-1002. Wesnousky, S., G., (2008), Displacement and Geometrical Characteristics of Earthquake Surface Ruptures: Issues and Implications for Seismic-Hazard Analysis and the Process of Earthquake Rupture, Bullettin of the Seismological Society of America, Vol. 98, No. 4, pp. 1609-1632, August 2008, doi:10.178/0120070111. Pavlides, S., R. Caputo, (2004), Magnitude versus faults’ surface parameters: quantitative relationships from the Aegean Region, Tectonophysics 380 (2004), 159-199. NEW CONSTRAINTS FOR FAULT SEGMENTATION, TECTONIC INVERSIONS AND EARTHQUAKE TRIGGERING MECHANISMS IN THE CENTRAL APENNINES NORMAL FAULT SYSTEM BY HIGH-RESOLUTION VELOCITY MODELS M. Buttinelli, G. Pezzo, L. Valoroso, P. De Gori, C. Chiarabba Istituto Nazionale di Geofisica e Vulcanologia The central Apennines (Italy) have a very complex structural architecture, mostly developed as a consequence of the overprint of different deformational phases. Such tectonic phases contributed in developing new peculiar structures as well as in reworking and segmenting previous geological structures, also repeatedly producing the conditions for episodic tectonic inversions. The reconstruction of the main geological structures and the discrimination between newly formed and reworked geologic features is therefore the key issue to unravel the seismotectonics of an area. This is also necessary because the geometry of large-scale discontinuities and their relationship with the active stress regime has a direct connection with large earthquakes nucleation, expected maximum magnitudes, aftershock occurrence and spreading, and strong implications for seismic hazard assessment in general. We present new velocity tomograms for the normal fault system activated during the 2009 and the 2016-2018 seismic sequences, showing how the principal crustal structures are currently interfering with the active extension. Moreover, we discuss on the relationship between the general crustal arrangement even at depth and the surficial expression of interpreted structures, which is still a question of strong debate within the scientific community. Finally, we investigate the possible interaction between the faults activated during the two sequences in terms of static stress changes induced by the nucleation of main events, proposing the fluid overpressure at depth as a viable mechanism behind the partial re-mobilization of unbroken segments of the fault system.