Integrating Multi-Resolution Seismic Reflection Data to Investigate Active Fault Geometry, Segmentation, and Evolution in Erdek Bay, Southwestern Marmara Sea

Erdek Bay, in the south western Sea of Marmara, lies along the Central Branch of the North Anatolian Fault system (NAF-C). This study integrates very high-resolution CHIRP, sparker, and high-resolution multi-channel seismic reflection (MCS) data with complementary resolution and penetration to investigate fault geometry, segmentation, and evolution. Seismic stratigraphic correlation with a well-tied regional section and time-structure mapping of four interpreted horizons (acoustic basement, base Pliocene, near-base Quaternary and ~9 ka) enable faults to be traced from the seafloor to the acoustic basement, and the results are summarized in a three-dimensional conceptual model. MCS data image basement-offsetting faults to ~1.3 s two-way travel time. Vertical separation generally decreases toward younger horizons and varies irregularly along strike, consistent with cumulative deformation and fault segmentation. Steep fault geometries, irregular along-strike variations in vertical separation, throw-direction reversal and regional tectonic constraints are compatible with possible oblique-slip components, although individual fault kinematics remain uncertain. Seismic-stratigraphic relationships suggest Pliocene fault activity potentially associated with development of the modern NAF-C tectonic regime; CHIRP and Sparker data document Holocene deformation along selected strands. Scenario-based magnitude estimates for four segments interpreted to offset H1 range from Mw 5.80 to 6.23 under individual-segment rupture assumptions. This multi-resolution approach improves characterization of distributed offshore fault systems.