GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 GNGTS 2023 A recent seismic coupling estimation for the Aegean - Anatolian region M. Palano 1 , F. Sparacino 1 , B. G. Galuzzi 2 , M. Segou 3 , C. Chiarabba 4 1 Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo - Sezione di Catania, Catania, Italy 2 Department of Biotechnology and Biosciences, University of Milan-Bicocca, Milan, Italy 3 British Geological Survey, The Lyell Center, Research Avenue South, EH14 4AP, Edinburgh, UK 4 Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Nazionale Terremoti, Roma, Italy We provide a novel estimation of the seismic coupling for the Aegean-Anatolian region by taking advantage of extensive seismic and geodetic datasets. Our approach estimate moment-rates and seismic coupling on 2° x 2° square cells with a 75% overlap and does not require an a priori zonation. To compute input parameters for the coupling estimation, such as the maximum expected magnitude, the seismogenic thickness and the coefficients of the frequency-magnitude distribution relation we compiled a set of historical and instrumental catalogs from existing seismicity records as well as an extensive combination of recent GNSS velocities integrated with recent literature solutions. Finally, the seismic coupling estimation enables characterizing the crustal deformation modality (seismic versus aseismic), as well as identifying potential seismic cycle gaps over the entire region, thereby providing additional constraints on modern seismic hazard estimates. In particular, seismic coupling is low (<35%) or intermediate (35% - 70%) in most of the study area, while the Karliova triple junction, a N-S-oriented belt along the boundary between western and central Anatolia, and the southeastern Peloponnese are fully coupled, suggesting a full seismic release of the measured deformation budget. Intermediate values of seismic coupling are observed for the eastern and central segments of the Northern and Eastern Anatolian Fault zones, where however the time period since the last large magnitude earthquakes clearly raises the possibility of impending earthquakes. Intermediate values of seismic coupling are also observed for part of the Hellenic volcanic arc, the Kefalonia Transform Fault and the Corinth gulf active faults. Here, considering the available historical records, these intermediate coupling values indicate either significant aseismic deformation or catalog incompleteness. A broad seismic gap is evidenced along the Hellenic subduction zone, because of the reduced coupling and the absence of ~M8 earthquakes in the last 700 years, at least. We conclude that in most of the central Aegean Sea aseismic deformation prevails as suggested by the small value of coupling and the modest seismic release over the last millennium.