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3D Wave Propagation Simulations of the 2019 M7.1 Ridgecrest, CA, Earthquake

Session: Physics-Based Earthquake Rupture Modeling and Strong Motion Simulations I

Type: Oral

Date: 4/22/2021

Presentation Time: 02:00 PM Pacific

Description: 

We have performed 3D numerical wave propagation simulations for the July 6 2019 M7.1 Ridgecrest, CA earthquake in a 200 km by 300 km model domain. The purpose of this study is to use a state-of-the-art 3D simulation tool to reproduce the broadband ground motions recorded close to the source and the greater Los Angeles area to better understand how different components of the model contribute to variability of broadband ground motions. We present the results of preliminary calculations up to 3 Hz with 500 m/s minimum shear wave velocity. The calculations were carried out on ORNL Summit using the newest version of the GPU-enabled AWP which enables calculations with surface topography on curvilinear grids. We used velocity and density information from the SCEC UCVM model CVM-S4.26.M01 with built-in geotechnical layers. We tested 3-segment source rupture models inverted from seismic and geodetic data with enhanced high frequency content, as well as one by the Graves-Pitarka kinematic rupture generator.

We find that, as expected, the effects of surface topography increase with frequency, reducing peak ground velocities (PGV) and prolonging the duration of shaking. In addition to topographic scattering, we find that small-scale heterogeneities of 5-10% strength are needed to predict the observed duration of shaking. The intrinsic attenuation model of Qs=0.1Vs, Qp=2Qs produced the least biased PGVs throughout our model domain. Finally, we find that a general underprediction of the PGVs by our simulations at rock sites can be alleviated by incorporating more accurate near-surface velocities.

Presenting Author: Te-Yang Yeh

Student Presenter: Yes

Authors