Near-fault velocity structure and ground motions of the 2019 M7.1 Ridgecrest earthquake

Te Yang Yeh

San Diego State University

Date & Time
Online-only seminar via Microsoft Teams
Evan Hirakawa

We have simulated 0–3 Hz deterministic wave propagation in the Southern California Earthquake Center Community Velocity Model (CVM) version CVM‐S4.26‐M01 for the 2019 Mw
7.1 Ridgecrest earthquake. A data‐constrained high‐resolution fault zone model (Zhou et al., 2022) is incorporated into the CVM to investigate the effects of the near‐fault low‐velocity zone (LVZ) on the resulting ground motions, constrained by strong‐motion data recorded at 161 stations. The finite‐fault source used for the simulation of the Ridgecrest event was obtained from the Liu et al. (2019) kinematic inversion, enriched by noise following a von Karman correlation function above ∼1 Hz with a f−2 high‐frequency decay. Our results show that the heterogeneous near‐fault LVZ inherent to the fault zone structure significantly perturbs the predicted wave field in the near‐source region, in particular by more accurately generating Love waves at its boundaries. The fault zone decreases the 0.1–0.5 Hz mean absolute Fourier amplitude spectrum bias to seismic recordings for all sites in the model and in the Los Angeles basin area (∼200 km from the source) by 16% and 26%, respectively. The fault zone structure generally improves modeling of the long‐period features in the data and lengthens the coda‐wave trains, in better agreement with observations. We recommend that a data‐constrained fault zone velocity structure, where available, be included in ground‐motion modeling to obtain the least‐biased fit to observed seismic data.

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