GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 - POSTER GNGTS 2023 Analysis of seismic deformation in the Adriatic Sea region B. Orecchio, D. Presti, S. Scolaro, C. Totaro Department of Mathematics, Computer Sciences, Physics, and Earth Sciences, University of Messina, Messina, Italy. The Adriatic Sea region is one of the most debated pieces of the tectonic puzzle of the Central Mediterranean plate margin for which several models of microplate fragmentation and kinematics have been proposed in the literature (e.g., Anderson and Jackson, 1987; D’Agostino et al., 2008; Perouse et al, 2012; Sani et al., 2016). In the past, seismic investigations of this marine area have been strongly hampered by uneven network geometries, but recent methodological improvements lay the groundwork to attempt more accurate analyses including proper evaluations of result reliability. On these grounds, we aimed at better characterize this area from the seismological point of view by furnishing new information on seismic source orientations, earthquake kinematics and seismogenic stress fields. We used the Bayloc non-linear probabilistic algorithm (Presti et al., 2004, 2008) to compute hypocenter locations for the most relevant seismic sequences by carefully evaluating location quality and seismolineaments reliability. We also provided an updated database of waveform inversion focal mechanisms including original solutions estimated by applying the waveform inversion method Cut And Paste (Zhao and Helmberger, 1994 and Zhu and Helmberger, 1996) and data available from official catalogs. Then, focal mechanism solutions have been used to estimate seismogenic stress fields through different inversion algorithms (Arnold and Townend, 2007; Vavry č uk 2014). Seismicity indicates a moderate activity mainly distributed in the Central Adriatic region and primarily related to thrust faulting. Here we identified five main sequences, occurred between 1986 and 2021, including several M ≥ 4 earthquakes and a maximum magnitude of 5.5. Focal mechanism solutions and seismogenic stress inversions revealed two main sectors with different seismic behavior located in the northeastern and southwestern portion of Central Adriatic, respectively. In particular, our analyses depicted two NW-SE oriented, adjacent volumes: (i) a pure compressive domain with NNE-trending axis of maximum compression characterizes the northeastern volume where the seismic activity occurs on W-to-NW oriented seismic sources; (ii) a transpressive domain with NW-trending axis of maximum compression characterizes the southwestern sector where thrust faulting preferentially occurs on ENE-to-NE oriented planes and strike-slip faulting on E-W ones. In this framework the spatial distribution of seismicity, the different source orientations and kinematics, and the above described stress field orientations