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Evaluation of the SCEC Seismic Velocity Models through Simulation and Validation of Past Earthquakes

Shima Azizzadeh-Roodpish, Ricardo Taborda, Naeem Khoshnevis, & Keli Cheng

Published 2015, SCEC Contribution #6222

SCEC scientists have devoted significant effort over the last two decades to the development of various seismic
velocity models for southern California. These models are mostly used in forward wave propagation simulation, but also as reference for tomographic and source inversions, and in other seismology and engineering problems. Two of these models, CVM-S and CVM-H, are among the most commonly used. This includes alternative variations such as the recently released model CVM-S4.26, which incorporates results from a sequence of tomographic inversions, and the user-controlled option of CVM-H to replace the near-surface profiles with a Vs30-based geotechnical layers (GTL) model. All four alternatives are thought acceptable, yet they have distinctions that lead to different results in forward simulations. The present study evaluates the accuracy of these models to predict the ground motion in the greater Los Angeles region through the validation of a series of past earthquake simulations. We present results for simulations of 30 moderate-magnitude earthquakes (3.5 < Mw < 5.5), and compare synthetics with data using a goodness-of-fit (GOF) method. The simulations are done with a finite element parallel code, with numerical models that satisfy a maximum frequency of 1 Hz and a minimum shear wave velocity of 200 m/s. We analyze the regional distribution of the GOF results for all events and all models, and search for correlations between the results and the characteristics of the models. Based on our comparisons, we identify which model consistently yields better results and present arguments that help explain why this is the case.

Azizzadeh-Roodpish, S., Taborda, R., Khoshnevis, N., & Cheng, K. (2015). Evaluation of the SCEC Seismic Velocity Models through Simulation and Validation of Past Earthquakes. Poster Presentation at 2015 SCEC Annual Meeting.