Garcia-Fernandez, Mariano ; Van Noten, Koen ; Jimenez, Maria-Jose ; Sakellariou, Nikolaos ; De Plaen, Raphael ; Kouskouna, Vasiliki ; Lecocq, Thomas ; Rodriguez-Diaz, Sara ; Galanos, Nikolaos

Poster presented at SSA2025, Denver, USA. on 2025-04-14

Abstract: Paliki Peninsula, the western end of Kefalonia Island, has been repeatedly hit by moderate to large earthquakes and is located in one of the most active seismotectonic regions of the Mediterranean Sea, to the east of the major Kefalonia-Lefkada transform fault. In 1953, an Mw 7.0 earthquake, preceded by two Mw 5.9 and Mw 6.6 foreshocks, produced extensive damage in Kefalonia. More recently, in 2014, a sequence with two main shocks (~ Mw 6.0) within eight days caused considerable damage and ground failure in the Paliki Peninsula. To develop a new 3D subsurface model for understanding site effects and to compute a more detailed velocity model for accurately locating earthquakes, a joint geophysical field campaign was organized in September 2024. During this campaign, we installed eight cross-profiles and one array through the Paliki Peninsula, using 24 SmartSolo IGU-16HR 3C nodes, three SmartSolo IGU-BD3C-5LC broadband devices and two Tromino instruments. Ambient noise measurements were carried out at 220 locations, resulting in 3225 hours of recorded ambient noise data, including recordings of tens of small earthquakes. Array- and cross-correlation techniques, and Horizontal to Vertical Spectral Ratios (HVSR) were applied to model the shallow sedimentary cover and variation in bedrock depth, for better understanding the impact of earthquakes on this area. Preliminary results show increasing thickness of Miocene marls deposits from west to east, overlaying a bedrock of Eocene limestones deeping towards the eastern shoreline of the peninsula, with a steeper attitude in the north. To our knowledge, this is the first time that such large-scale fieldwork has been performed on the Ionian Islands and the recorded data will stimulate new research studies, contributing significantly to more precise earthquake locations, and more accurate local hazard assessments and risks evaluations.

Keyword(s): HVSR ; Kefalonia ; Greece ; Site effects