From 1997 to 2000, seismic reflection data from the California Continental Borderland were acquired to identify the active fault systems in the southern California offshore area. The studies focused on the coastal zone, which includes the shelf, slope, and adjacent basinal areas, that poses the greatest potential seismic hazards for the most populated urban corridor along the U.S. Pacific margin. A major goal is to understand the fault-slip history of, and current strain along, the active (defined as Holocene age) faults to determine the hazard potential. In addition, the history of landslide generation is a related focus of the study to determine the potential for generation of tsunamis that can devastate the coastal area. The primary objective has been to help mitigate the earthquake hazards for the southern California region by improving our understanding of how deformation is distributed (spatially and temporally) across the offshore as well as the onshore regions.

Studies under the Earthquake Hazard Task (the Tierra component of the CABRILLO Project) focused on imaging the nearshore fault systems and developing a detailed stratigraphic framework to understand the late Quaternary history of sedimentation and deformation patterns in the California Continental Borderland (Figure 1). In addition, seismic-reflection imaging can provide the subsurface dimensions of the faults and identify the size and frequency of submarine landslides, both of which are necessary for evaluating the potential for generating destructive tsunamis in the southern California offshore. In order to evaluate the strain associated with the offshore structures, the results from the seismic-reflection profiling conducted under this project will be used to identify possible sites for deployment of acoustic geodetic instruments to monitor strain in the offshore region. A major goal of mapping under this project is to provide detailed geologic and geophysical information in GIS data bases that build on the earlier studies and use the new data to precisely locate active faults and to map recent submarine landslide deposits.

The following sections present the trackline locations, which can be used to link the reader directly to images of the seismic-reflection profiles; in addition, tables are provided that will allow downloading the graphical images (both TIFF and JPEG formats) as well as SEG-Y formatted data.