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3D Seismic Velocity Model for the Eel River Basin Region and Ground-Motion Simulations for the 2022 Mw6.4 Ferndale, California Earthquake

Description: 

We simulate 3D seismic wave propagation from the 2022 Mw 6.4 Ferndale, California earthquake and compare synthetic ground motions (<2 Hz) with recordings. The simulations use a 3D seismic velocity structure obtained by embedding a model of the Eel River Basin into the USGS San Francisco Bay region 3D seismic velocity model – regional domain (SFCVM-R). The basin model consists of a 2D bedrock-depth surface which was originally interpolated by Graves (1994) from cross sections drawn by Ogle (1953). We insert this as a new surface into the regional 3D geologic model and fill the basin with properties appropriate for Quaternary sediments. We model three moderate earthquakes (Mw<4.5) with hypocenters close to the 2022 earthquake as point sources and compare synthetics with recordings in order to test the velocity model.

We model the 2022 Ferndale earthquake source as a left-lateral rupture propagating unilaterally to the east, with our preliminary models using an assumed randomized slip distribution generated using the Graves and Pitarka (2016) approach. Synthetic ground motions are significantly amplified in the low velocity Eel River Basin, where >1g acceleration was recorded and MMI VIII shaking was experienced. We interpret the amplification of ground motions to result from a combination of rupture directivity and basin response effects.

Session: Multi-scale Models for Seismic Hazard Analysis

Type: Oral

Date: 4/20/2023

Presentation Time: 03:00 PM (local time)

Presenting Author: Evan Hirakawa

Student Presenter: No

Invited Presentation: 

Authors