A Robust Tsunami Deposit Database For California

The California Geological Survey (CGS) has partnered with Humboldt State University (HSU) to produce a robust statewide tsunami deposit database to facilitate the evaluation of tsunami hazard products for both emergency response and land-use planning and development. The California tsunami deposit database attributes compliment and expand on existing tsunami deposit databases from the National Geophysical Data Center (NGDC) (Global), the USGS (Cascadia Subduction Zone), and the Oregon Department of Geology and Mineral Industries (DOGAMI) (adjacent state). Whereas the existing NGDC and USGS databases focus on references or individual tsunami layers, this new State-maintained database concentrates on the location and contents of individual cores/trenches that sample tsunami deposits, including laboratory tests to evaluate sample grain-size, geochemistry, microfossils, and age-dating results. The first generation of the database is completed and includes 94 cores from six studies in northern California, at the southern end of the Cascadia Subduction Zone. A second generation of the database will include recently collected tsunami deposit information for the rest of California. These data provide an important observational benchmark for evaluating the results of tsunami inundation modeling. CGS is collaborating with and sharing the database entry form with other states to encourage its continued development beyond California's coastline so that tsunami deposits can be more easily evaluated on a regional basis, a recommendation of the National Tsunami Hazard Mitigation Program. This database is being used to help CGS in the development and validation of updates to their existing inundation maps for emergency planning, and probabilistic tsunami hazard analyses (PTHA) of value to local land-use planning and coastal development.