Lateral Variations Across the Southern San Andreas Fault Zone Revealed From Analysis of Traffic Signals at a Dense Seismic Array

Journal Article · Tue Jul 11 00:00:00 EDT 2023 · Geophysical Research Letters

DOI:https://doi.org/10.1029/2023GL103759· OSTI ID:1989418

Zhang, Hao  ^[1]; Meng, Haoran  ^[2]; Ben‐Zion, Yehuda  ^[3]

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1. University of Southern California Los Angeles CA USA
2. Southern University of Science and Technology Shenzhen China
3. University of Southern California Los Angeles CA USA, Southern California Earthquake Center Los Angeles CA USA

Abstract We image the shallow seismic structure across the Southern San Andreas Fault (SSAF) using signals from freight trains and trucks recorded by a dense nodal array, with a linear component perpendicular to SSAF and two 2D subarrays centered on the Banning Fault and Mission Creek Fault (MCF). Particle motion analysis in the frequency band 2–5 Hz shows that the examined traffic sources can be approximated as moving single‐ or multi‐point sources that primarily induce Rayleigh waves. Using several techniques, we resolve strong lateral variations of Rayleigh wave velocities and Q ‐values across the SSAF, including 35% velocity reduction across MCF toward the northeast and strong attenuation around the two fault strands. We further resolve 10% mass density reduction and 45% shear modulus decrease across the MCF. These findings suggest that the MCF is currently the main strand of the SSAF in the area with important implications for seismic hazard assessments.

• Sponsoring Organization: USDOE
• Grant/Contract Number: ED‐SC0016520
• OSTI ID: 1989418
• Alternate ID(s): OSTI ID: 1989420
• Journal Information: Geophysical Research Letters, Journal Name: Geophysical Research Letters Vol. 50 Journal Issue: 14; ISSN 0094-8276
• Publisher: American Geophysical Union (AGU)
• Country of Publication: United States
• Language: English