This research is to use existing high-resolution seismic reflection profiles and earthquake data with bathymetry and gravity measurements to study a region offshore southern California. In this active seismic area, the objective will be to delineate structures that are currently deforming and correlate them with locations of earthquakes. This area includes the site of the offshore 1986 M=5.8 Oceanside earthquake. The results will help to determine if the identification of active deformation structures can be used to estimate seismic hazard. This research is a component of the National Earthquake Hazard Reduction Program.