Determination of Near Surface Shear-Wave Velocities in the Central Los Angeles Basin With Dense Arrays

Creators: Jia, Zhe; Clayton, Robert W.

Abstract

In this study, we investigate the shallow shear wave velocity structure of the Los Angeles Basin in southern California, using ambient noise correlations between 5 dense arrays and 21 broadband stations from the Southern California Seismic Network (SCSN). We observe clear fundamental mode and first overtone Rayleigh waves in the frequency band 0.25–2.0 Hz, and obtain group velocity maps through tomography. We further derive a 3D shear wave velocity model, covering a large portion of the central LA Basin for the depths shallower than 3 km. We found that the small scale shallow velocity structure heterogeneities are better resolved compared with the SCEC Community velocity models. Our model captures the presence of the Newport‐Inglewood fault by a NW–SE trending high velocity belt. Our model provides more accurate constraints on local ground motion predictions with detailed mapping of structural heterogeneities.

Additional Information

© 2021 American Geophysical Union. Issue Online: 03 May 2021; Version of Record online: 03 May 2021; Accepted manuscript online: 20 April 2021; Manuscript accepted: 14 April 2021; Manuscript revised: 09 April 2021; Manuscript received: 14 November 2020. The authors gratefully thank reviewer Yixiao Sheng, an anonymous reviewer, associate editor Nori Nakata and editor Yehuda Ben‐Zion for their constructive comments and suggestions. The authors gratefully thank Signal Hill Petroleum for providing permission to use the ambient noise data for the Long Beach (LB3D), Extended Long Beach (ELB) arrays, Breitburn Energy for the use of the Santa Fe Springs and Rosecrans arrays, and LA Seismic for providing the Seal Beach array. Access to the raw data requires permission from these owners. The authors thank Jorge C. Castellanos for helpful discussions. This project is supported by NSF/EAR‐15200081. Data Availability Statement: The Rayleigh wave group velocity dispersion data used to generate the final velocity model can be downloaded from: http://doi.org/10.22002/D1.1670. The final LAS1 wave velocity model can also be downloaded from that site. The authors thank the Southern California Earthquake Data Center for providing public access to the broadband seismic ambient noise data (https://scedc.caltech.edu).

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Supplemental Material - downloadSupplement_doi=10.1029_2F2020JB021369_file=2020JB021369-sup-0001-Supporting+Information+SI-S01.docx

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