Evaluation of the Southern California Seismic Velocity Models through Simulation of Recorded Events

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

Published 2016, SCEC Contribution #6150

Significant effort has been devoted over the last two decades to the development of various seismic velocity models for the region of southern California, United States. These models are mostly used in forward wave propagation simulation studies, but also as base models for tomographic and source inversions. Two of these models, the community velocity models CVM-S and CVM-H, are among the most commonly used for this region. This includes two alternative variations to the original models, the recently released CVM-S4.26 which incorporates results from a sequence of tomographic inversions into CVM-S, and the user-controlled option of CVM-H to replace the near-surface profiles with a Vs30-based geotechnical (GTL) model. Although either one of these models is regarded as acceptable by the modeling community, it is known that they have differences in their representation of the crustal structure and sedimentary deposits in the region, and thus can lead to different results in forward and inverse problems. In this article we evaluate the accuracy of these models when used to predict the ground motion in the greater Los Angeles region through the validation of a collection of simulations of historical events. In total, we consider 30 moderate-magnitude earthquakes (3.5 < Mw < 5.5), and compare synthetics with data recorded by seismic networks during these events. The simulations are done using 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. The comparisons between data and synthetics are ranked quantitatively by means of a goodness-of-fit (GOF) criteria. We analyze the regional distribution of the GOF results for all events and all models, and draw conclusions from the results and how these correlate to the characteristics of the models. We find that, in light of our comparisons, one of the models consistently yields better results and explore the reasons leading to this conclusion.

Taborda, R., Azizzadeh-Roodpish, S., Khoshnevis, N., & Cheng, K. (2016). Evaluation of the Southern California Seismic Velocity Models through Simulation of Recorded Events. Geophysical Journal International, 205(3), 1342-1364.