Northern California 3D seismic velocity models and earthquake ground motion simulations

Earthquake Science Center Seminars

Evan Hirakawa, USGS

Northern California, specifically the San Francisco Bay Area, is a great place to study earthquake hazards and risk, due to its dense population centers surrounded by active faults, as well as complex geology that strongly influences earthquake ground motions. Computer simulations of seismic wave propagation which can incorporate 3D models of the subsurface properties and complex faulting behavior are good tools for studying seismic hazard, but ultimately require more development before unlocking full potential; specifically, the 3D seismic velocity models need to be further developed in many places and the simulated motions need to be validated with real, recorded data.

In this talk, I will summarize a few different research projects on these topics. First I will review recent efforts to improve the USGS San Francisco Bay region 3D seismic velocity model (SFCVM), the leading community velocity model in the area, and describe some of its interesting features. This will be followed by a preview of ongoing work from collaborators and some other promising avenues to explore, in hopes of further improving the model and stoking more community involvement. In the second part of the talk, I will switch gears and move farther north, to the Humboldt County area, where a recent M7 earthquake occurred offshore. I will show some preliminary modeling results, discuss the datasets available from this event, and describe some of the local geology and efforts to better understand subsurface structure.