GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 GNGTS 2023 The seismicity in the central Adriatic Sea has been recorded by the improving seismic network, especially in recent decades. Since 1985, the ISIDe catalog (http://terremoti.ingv.it) lists 6 seismic events with M>4.5 that occurred in the central Adriatic region (40 km off-shore), four of them belonging to the Jabuka 2003 seismic sequence (Herak et al., 2005), confirming that the seismic potential of this area is significantly higher than that assumed until some time ago. Nevertheless, the precise location of the Adriatic off-shore earthquakes was hampered in both historical and instrumental seismology times due to almost exclusive resentment along the coast with consequent poor documentation, and to the large gap in the distribution of seismic stations, respectively. Starting from the 1986-1990 seismic sequences (Console et al., 1993), the Adriatic region saw a new motivating force on the investigation of its geodynamics, even if the hypocenter location difficulty still remains. The sP depth phases enable us to estimate more accurately the epicentral parameters and focal depths of these earthquakes and to depict with high precision the geometry of the fault activated (Fig. 2; Fig. 3). The mainshock originated at a focal depth of 9.9 km. The seismicity spreads from the mainshock up-dip and down-dip along a NE dipping plane. The refined earthquake locations allow us to make inferences on the seismotectonic context responsible for the seismicity, identifying this structure (here referred to as the Mid-Adriatic Fault, MAF) as a thrust fault NW-SE striking and ~45° NE-dipping. References BSI, ISIDe Working Group; 2007: Italian Seismological Instrumental and Parametric Database (ISIDe). Istituto Nazionale di Geofisica e Vulcanologia (INGV). <https://doi.org/10.13127/ISIDE> Console, R., R. Di Giovambattista, P. Favali, B.W. Presgrave and G. Smriglio; 1993: S eismicity of the Adriatic microplate . Tectonophysics 218 (4). Di Stefano R., Ciaccio M. G., Baccheschi P. and Zhao D.; 2022: The Adriatic Thrust Fault of the 2021 Seismic Sequence Estimated from Accurate Earthquake Locations Using sP Depth Phases . Bull. Of Seism. Soc., Dec 2022, https://doi.org/10.1785/0120220111 Herak, D., M. Herak, E. Prelogovi ć , S. Marku š i ć , and Ž . Markulin; 2005: Jabuka island (Central Adriatic Sea) earthquakes of 2003 . Tectonophysics 398 (3 – 4), pp. 167 - 180, https://doi.org/10.1016/j.tecto.2005.01.007 Ivan č i ć , I., D. Herak, M. Herak, I. Allegretti, T. Fiket, K. Kuk, S. Marku š i ć , S. Prevolnik, I. Sovi ć , I. Dasovi ć and J. Stip č evi ć ; 2018: Seismicity of Croatia in the period 2006–2015 . Geofizika 35, doi:10.15233/gfz.2018.35.2. Latorre, D., R. Di Stefano, B. Castello, M. Michele and L. Chiaraluce; 2022: A global image of the Italian seismicity from a 3D probabilistic nonlinear inversion of instrumental data: the 1981-2018