Title: Peak Ground Velocity Spatial Variability Revealed by Dense Seismic Array in Southern California

Abstract

Abstract Understanding and modeling variability of ground motion is essential for building accurate and precise ground motion prediction equations, which can net site‐specific characterization and reduced hazard levels. Here, we explore the spatial variability in peak ground velocity (PGV) at Sage Brush Flats along the San Jacinto Fault in Southern California. We use data from a dense array (0.6 × 0.6 km ² , 1,108 geophones, station spacings 10–30 m) deployed in 2014 for ~1 month. These data offer an opportunity to study small‐scale variability in this region. We examine 38 earthquakes (2 ≤ M _L  ≤ 4.2) within 200 km of the array. Fault strands and a small basin impact the ground motions, producing PGV variations up to 22% of the mean and a 40% reduction in P and S wave near‐surface velocities. We find along‐fault rupture directivity, source, and path effects can increase PGVs by 167%. Surface PGV measurements exceed the colocated borehole station (depth at 148 m) PGV by factors of 3–10, confirming the impact on PGV from near‐surface fault structures, basins, topography, and amplifications from soft sediments. Consistently, we find high PGVs within the basin structure. A pair of colocated GaM _L 2.6 events produce repeatable PGV values with similar spatial patterns. The average corner frequenciesmore » of these two events are 11–16 Hz, and viable measurements of stress drop can differ by 6.45 MPa. Within this small array, the PGV values are variable implying spatial extrapolation of PGV to regions of known faults and basins, even across a small area, should be done with caution.« less

Authors:

Johnson, Christopher W.  ^[1];

• Search DOE PAGES for author "Johnson, Christopher W."
• Search DOE PAGES for ORCID "0000-0002-2589-7593"

Kilb, Debi  ^[1];

• Search DOE PAGES for author "Kilb, Debi"
• Search DOE PAGES for ORCID "0000-0002-7252-4167"

Baltay, Annemarie  ^[2];

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• Search DOE PAGES for ORCID "0000-0002-6514-852X"

Vernon, Frank  ^[1]

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• Search DOE PAGES for ORCID "0000-0002-9379-4000"

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+ Show Author Affiliations

1. Scripps Research Institute, San Diego, CA (United States)
2. US Geological Survey, Moffett Field, CA (United States)

Publication Date:

Mon Jun 01 00:00:00 EDT 2020

Research Org.:

Univ. of Southern California, Los Angeles, CA (United States); Univ. of California, San Diego, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1803023

Alternate Identifier(s):

OSTI ID: 1633941

Grant/Contract Number:  

SC0016520; SC0016527; DE‐SC0016520; DE‐SC0016527

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Geophysical Research. Solid Earth

Additional Journal Information:

Journal Volume: 125; Journal Issue: 6; Journal ID: ISSN 2169-9313

Publisher:

American Geophysical Union

Country of Publication:

United States

Language:

English

Subject:

58 GEOSCIENCES; Geochemistry & Geophysics