A Comprehensive Offshore Quaternary Fault Database for California

Date: 4/24/2019

Time: 06:00 PM

Room: Grand Ballroom

In the last decade, a number of new marine geophysical datasets collected by the U.S. Geological Survey (USGS), the Ocean Exploration Trust, and other organizations has led to substantially improved high-resolution mapping of the seafloor in areas including California's mainland State Waters and the southern California continental borderland. Data include comprehensive multibeam bathymetry, seismic-reflection, and marine magnetic data in numerous offshore areas. Most of these data have been processed, merged, and released by the USGS in maps, data releases, and journal publications in support of the California Seafloor Mapping Program and the U.S. West Coast and Alaska Marine Geohazards Project. Improved data coverage has allowed researchers to better map offshore faults in areas previously unmapped or covered only by low-resolution data. Additionally, subsurface imaging and seafloor sampling has led to better understanding of fault kinematics and recency of deformation, which are highly relevant for assessing California's seismic and coastal hazards. For example, inclusion of updated offshore faults resulted in a 37% increase in calculated seismic hazard for the San Diego area in a 2015 rupture forecast.

Here, we present a fault geodatabase with comprehensive metadata including accurate locations, geometries, ages, slip rates, and relevant published references. This represents a significant update to previous national and regional fault compilations, developed without the benefit of new high-resolution datasets. The geodatabase has been designed for easy ingestion by partners including the California Geological Survey and the USGS Quaternary Fault and Fold Database, and to be used to improve seismic hazards products, especially the USGS National Seismic Hazard Maps and the Uniform California Earthquake Rupture Forecast. Other stakeholders include the Southern California Earthquake Center and the academic and consulting communities. We plan to expand this effort in the near future to include work now in progress in other regions offshore of the Pacific Northwest and Alaska.

Presenting Author: Antoinette G. Papesh

Authors