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Ambient noise differential adjoint tomography reveals fluid-bearing rocks near active faults in Los Angeles.

ABSTRACT: Water scarcity is a pressing issue in California. We develop ambient noise differential adjoint tomography that improves the sensitivity to fluid-bearing rocks by canceling bias caused by noise sources. Here we image the shallow S-wave velocity structure using this method beneath a linear seismic array (LASSIE) in Los Angeles Basin, which shows significant velocity reduction marking a major regional water producer, the Silverado aquifer, along with other fluid-bearing structures. Based on the S-wave tomography and previous P-wave studies, we derive the porosity in Long Beach and discover that the rock from 1-2 km depth surrounding the Newport-Inglewood Fault contains abundant fluids with pore-fluid fraction ~0.33. The high-porosity rock around the fault coincides with previously observed week-long shallow seismicity south of LASSIE array in Long Beach. The imaged S-wave velocity in the top layer shows a similar trend in the geotechnical layer Vs 30, suggesting additional applications to ground motion prediction.

SUBMITTER: Liu X

PROVIDER: S-EPMC10613219 | biostudies-literature | 2023 Oct

REPOSITORIES: biostudies-literature

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Ambient noise differential adjoint tomography reveals fluid-bearing rocks near active faults in Los Angeles.

Liu Xin X Beroza Gregory C GC Li Hongyi H

Nature communications 20231028 1

Water scarcity is a pressing issue in California. We develop ambient noise differential adjoint tomography that improves the sensitivity to fluid-bearing rocks by canceling bias caused by noise sources. Here we image the shallow S-wave velocity structure using this method beneath a linear seismic array (LASSIE) in Los Angeles Basin, which shows significant velocity reduction marking a major regional water producer, the Silverado aquifer, along with other fluid-bearing structures. Based on the S- ...[more]

PMID: 37898624

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Ambient noise differential adjoint tomography reveals fluid-bearing rocks near active faults in Los Angeles.

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Ambient noise differential adjoint tomography reveals fluid-bearing rocks near active faults in Los Angeles.

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