3D Wave Propagation Simulations of m6.5+ Earthquakes on the Tacoma Fault Considering the Effects of Topography, a Geotechnical Layer and a Near-fault Damage Zone
The U.S. Geological Survey's 3-D Cascadia Seismic Velocity Model (CVM) is commonly used to describe Earth structure when simulating earthquakes in western Washington, Oregon and Northern California. By considering results from seismic tomography surveys and regional geologic mapping, the CVM reasonably constrains seismic velocity throughout the region. However, the model does not include a geotechnical layer and has only rudimentary shallow (<100 m depth) velocity information. In preparation for high frequency (>1 Hz), direct earthquake simulations, we make targeted updates to the CVM to account for greater near-surface and near-fault complexity. These updates include adding surface topography, a shallow, low-velocity (~100 m/s) geotechnical layer, and near-fault damage zones. The updates are made in addition to imposing a frequency-independent attenuation model and small-scale, S-wave velocity heterogeneity throughout the shallow crust. We investigate the impact of these changes by simulating a suite of M6.5+, kinematic rupture scenarios on the Tacoma Fault, a crustal reverse fault in Washington State’s Puget Sound region. Simulations are run in 3-D using a spectral element method code (SPECFEM3D) on a mesh with a finely sampled topographic surface. The resulting ground motions can be resolved up to 3 Hz. We compare simulated ground motions between the different iterations of the CVM to one another and validate them against the empirically predicted peak ground motions from the 2014 NGA-West2 ground motion models. The results from this work provide a framework for updated seismic hazard analysis and direct earthquake simulation in the Pacific Northwest.
Session: Development, Enhancement and Validation of Seismic Velocity Models [Poster]
Type: Poster
Room: Evergreen Ballroom
Date: 4/21/2022
Presentation Time: 08:00 AM Pacific
Presenting Author: Ian Stone
Student Presenter: No
Additional Authors
Ian Stone Presenting Author Corresponding Author istone@usgs.gov U.S. Geological Survey |
Erin Wirth emoriarty@usgs.gov U.S. Geological Survey |
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3D Wave Propagation Simulations of m6.5+ Earthquakes on the Tacoma Fault Considering the Effects of Topography, a Geotechnical Layer and a Near-fault Damage Zone
Category
Development, Enhancement and Validation of Seismic Velocity Models
Description