Seminar Room / Online

23 Juni 2026

Gianmaria Bocchini - Institute of Geosciences, Ruhr University of Bochum, Bochum, Germany

15:30

The western Peloponnese exhibits a complex, transitional stress field near the western termination of the Hellenic Subduction System. Using an integrated permanent and temporary seismic network operating between December 2023 and September 2024, we constructed a high-precision earthquake catalog (Mc ≈ 1) to investigate the driving mechanisms of seismicity and the stress field across the plate boundary. In the upper plate, seismicity styles vary rapidly over short distances: tectonic loading drives strike-slip deformation and mainshock–aftershock sequences in the northwestern Peloponnese (near Vartholomio), whereas fluid-driven pore-pressure changes likely control migrating earthquake swarms along north–south-trending normal faults in the central-western Peloponnese (near Zacharo). Cluster analysis further reveals elevated background seismicity rates and greater seismic moment release in the north, consistent with a north-to-south decrease in strain rates. Total seismic moment release is dominated by the 29 March 2024 Mw 5.9 earthquake sequence offshore of the Strofades Islands. High-precision relocations and focal mechanisms suggest an intraslab origin for the sequence, which ruptured a NNE–SSW-striking left-lateral strike-slip fault. The associated stress regime reflects NNW–SSE arc-parallel shortening, in contrast to the regional NE–SW plate convergence indicated by GNSS velocity vectors and shallow focal mechanisms. The contrasting stress fields observed in the upper and lower plates, together with the absence of triggered upper-plate seismicity, suggest a decoupled upper–lower plate stress regime best explained by a weak megathrust interface.