Quaternary fault traces of the U.S. Cascadia subduction zone offshore northern California, Oregon, and Washington

A map of Quaternary faults has been generated for the offshore part of the U.S. Cascadia subduction zone in Federal and Tribal waters along the outer coast of northern California, Oregon, and Washington. These data contain lines representing the location of faults with known or suspected Quaternary (<2,580,000 years) activity. This fault map includes newly identified and modified traces and geometries for offshore faults from recent peer-reviewed studies that employ integrated analysis of 30-m resolution gridded multibeam bathymetry, systematic margin-wide coverage of shipborne seismic, and targeted autonomous underwater vehicle (AUV) multibeam and chirp data. This dataset was compiled as part of the USGS Subduction Zone Marine Geohazards Project to update and document potential earthquake and tsunami sources for hazard assessment and modeling in the Cascadia subduction zone. This product fills an important data gap outlined in the USGS Subduction Zone Science Plan (Gomberg et al., 2017). In the last decade, several new marine geophysical datasets collected by the U.S. Geological Survey (USGS), the Cascadia Seismic Imaging Experiment 2021 (CASIE21), and the Expanding Pacific Research and Exploration of Submerged Systems (EXPRESS) campaign has led to substantially improved systematic and high-resolution mapping of the seafloor and sub-seafloor offshore the Cascadia subduction zone. Comprehensive data coverage over multiple spatial scales enables systematic structural characterization of late Quaternary and Holocene upper plate deformation that is critical for accurately assessing subduction zone earthquake and tsunami hazards. This map contains 1) lines representing the locations of faults with known or suspected Quaternary (<2,580,000 years) activity and 2) points along those lines where fault dip is constrained by depth-migrated seismic data. This compilation represents an update to previous national and regional fault datasets that have been developed largely without high-resolution shipborne and AUV datasets and it is intended to be revised as necessary. The GIS shapefiles have been structured for incorporation in hazard assessment and modeling products, including the USGS National Seismic Hazard Maps, the Uniform California Earthquake Rupture Forecast, the Cascadia Region Earthquake Science Center (CRESCENT) Community Fault Model, and the Southern California Earthquake Center (SCEC) Community Fault Model. Other stakeholders include state agencies, academic scientists, consultants, community planners and managers, the risk assessment community, and the public. All marine geophysical data used for mapping have been released by the USGS and collaborators in maps, data releases, and journal publications and are listed in the files provided below. Reference: Gomberg, J.S., Ludwig, K.A., Bekins, B.A., Brocher, T.M., Brock, J.C., Brothers, Daniel, Chaytor, J.D., Frankel, A.D., Geist, E.L., Haney, Matthew, Hickman, S.H., Leith, W.S., Roeloffs, E.A., Schulz, W.H., Sisson, T.W., Wallace, Kristi, Watt, J.T., Wein, Anne, 2017, Reducing risk where tectonic plates collide--U.S. Geological Survey subduction zone science plan: U.S. Geological Survey Circular 1428, 45 p., https://doi.org/10.3133/cir1428.