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Ground motions in urban Los Angeles from the 2019 Ridgecrest earthquake sequence

Filippitzis, Filippos and Kohler, Monica D. and Heaton, Thomas H. and Graves, Robert W. and Clayton, Robert W. and Guy, Richard G. and Bunn, Julian J. and Chandy, K. Mani (2021) Ground motions in urban Los Angeles from the 2019 Ridgecrest earthquake sequence. Earthquake Spectra, 37 (4). pp. 2493-2522. ISSN 8755-2930. doi:10.1177/87552930211003916.

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We study ground-motion response in urban Los Angeles during the two largest events (M7.1 and M6.4) of the 2019 Ridgecrest earthquake sequence using recordings from multiple regional seismic networks as well as a subset of 350 stations from the much denser Community Seismic Network. In the first part of our study, we examine the observed response spectral (pseudo) accelerations for a selection of periods of engineering significance (1, 3, 6, and 8 s). Significant ground-motion amplification is present and reproducible between the two events. For the longer periods, coherent spectral acceleration patterns are visible throughout the Los Angeles Basin, while for the shorter periods, the motions are less spatially coherent. However, coherence is still observable at smaller length scales due to the high spatial density of the measurements. Examining possible correlations of the computed response spectral accelerations with basement depth and Vs30, we find the correlations to be stronger for the longer periods. In the second part of the study, we test the performance of two state-of-the-art methods for estimating ground motions for the largest event of the Ridgecrest earthquake sequence, namely three-dimensional (3D) finite-difference simulations and ground motion prediction equations. For the simulations, we are interested in the performance of the two Southern California Earthquake Center 3D community velocity models (CVM-S and CVM-H). For the ground motion prediction equations, we consider four of the 2014 Next Generation Attenuation-West2 Project equations. For some cases, the methods match the observations reasonably well; however, neither approach is able to reproduce the specific locations of the maximum response spectral accelerations or match the details of the observed amplification patterns.

Item Type:Article
Related URLs:
URLURL TypeDescription
Filippitzis, Filippos0000-0001-8377-4914
Kohler, Monica D.0000-0002-4703-190X
Heaton, Thomas H.0000-0003-3363-2197
Graves, Robert W.0000-0001-9758-453X
Clayton, Robert W.0000-0003-3323-3508
Guy, Richard G.0000-0002-8651-5608
Bunn, Julian J.0000-0002-3798-298X
Chandy, K. Mani0000-0001-9190-1290
Additional Information:© The Author(s) 2021. Article first published online: April 28, 2021; Issue published: November 1, 2021. Received: February 09, 2021; Accepted: February 22, 2021. We acknowledge the Texas Advanced Computing Center (TACC) at The University of Texas at Austin ( for providing high-performance computing resources through an allocation to the Southern California Earthquake Center (SCEC). We thank John H. Shaw and Andreas Plesch for providing assistance in obtaining the regional basement topography data. The authors appreciate the constructive reviews of the manuscript provided by Morgan Page and Grace Parker. The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: We are grateful to Caltech, the Betty and Gordon Moore Foundation, the Conrad N. Hilton Foundation, and Computers & Structures, Inc., for funding this project and for supporting the continuous operation of the Community Seismic Network. This research was also supported by the Southern California Earthquake Center (Contribution No. 10931). SCEC is funded by NSF Cooperative Agreement EAR-1600087 & USGS Cooperative Agreement G17AC00047. The first author was supported by the Cecil and Sally Drinkward Graduate Fellowship at the California Institute of Technology. The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Group:Seismological Laboratory
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
Conrad N. Hilton FoundationUNSPECIFIED
Computers & Structures, IncUNSPECIFIED
Southern California Earthquake Center (SCEC)10931
Cecil and Sally Drinkward FellowshipUNSPECIFIED
Subject Keywords:Earthquake ground motions, ground motion amplification, community seismic network, Ridgecrest earthquake sequence, simulation predictions, GMPE predictions
Issue or Number:4
Record Number:CaltechAUTHORS:20211209-231200000
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112353
Deposited By: George Porter
Deposited On:10 Dec 2021 20:24
Last Modified:01 Feb 2022 22:54

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