Preliminary Results of Multigeophysical Studies in the Edremit Basin (Balikesir), Northwestern Türkiye

This study presents preliminary results from a multidisciplinary geophysical investigation conducted in the Edremit Basin (Balıkesir), Northwestern Türkiye, as part of TÜBİTAK Project No. 123Y151. The region has experienced significant seismic events, including the 1944 Edremit Gulf (Ms=6.8) and the 1953 ienice-Gönen (Ms=7.2) earthquakes. To assess seismic hazard and dynamic soil behavior, various methods were employed, including MASW, ReMi, seismic P-wave refraction, SPAC, microgravity, and single-station microtremor measurements. These techniques aim to determine the subsurface structure and the soil-bedrock interface in 1D, 2D, and 3D. The study area was divided into sub-regions such as Edremit, Havran, Burhaniye for detailed investigation. In the initial phase, microtremor, seismic, and microgravity data were collected and analysed across the basin to understand the soil conditions on a regional scale. In this step, data processing included H/V spectral ratio analysis (Nakamura Method), dispersion curve inversion, and P- and S-velocities-depth profiling. We performed an integration of active and passive surface wave methods allowed for improved resolution of shear wave velocities. In addition, geological data, such as digital elevation models and orthophotos, were used to characterize structural features and fault zones. These preliminary results lay the groundwork for ongoing site-specific seismic hazard assessments in the Edremit Basin.