CLASSIFYING MARINE FAULTS FOR HAZARD ASSESSMENT OFFSHORE ISRAEL: A NEW APPROACH BASED ON FAULT SIZE AND VERTICAL DISPLACEMENT

Offshore geohazard mitigation methodologies often lag behind well-established onshore practices, particularly in assessing fault hazards in marine environments. Determining fault activity requires ultra-high-resolution seismic surveys and multiple coring, often yielding uncertain results. Moreover, slip rates are crucial for resistant planning when a pipeline must cross a fault. This study proposes a new approach to fault hazard assessment for infrastructure master planning, enabling planners to select routes crossing the least hazardous faults, which can then be investigated in site-specific surveys for slip rates and seismic design. By leveraging the abundance and quality of marine seismic data, we measure the recent (350 ka) vertical displacement and plane size of each fault in the study area using existing industrial 3D seismic surveys. Faults are classified into three hazard levels based on these independently measured quantities, creating a fault hazard level map for planners. Our case study focuses on the Israeli continental slope, where numerous salt-related, thin-skinned, normal faults dissect the seabed, forming tens of meters high scarps. A particularly hazardous zone is identified on the upper slope south of the Dor disturbance, where large listric faults rupture the seabed in an area with a sedimentation rate four times faster than the displacement rate, potentially indicating exceptionally fast creep, seismic rupture, or rapid tremor and slip episodes.