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Fault Zone Imaging with Distributed Acoustic Sensing: Surface-to-Surface Wave Scattering
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  • Yan Yang,
  • Zhongwen Zhan,
  • Zhichao Shen,
  • James Atterholt
Yan Yang
California Institute of Technology

Corresponding Author:[email protected]

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Zhongwen Zhan
California Institute of Technology
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Zhichao Shen
California Institute of Technology
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James Atterholt
California Institute of Technology
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Abstract

Fault zone complexities contain important information about earthquake physics. High-resolution fault zone imaging requires high-quality data from dense arrays and new seismic imaging techniques that can utilize large portions of recorded waveforms. Recently, the emerging Distributed Acoustic Sensing (DAS) technique has enabled near-surface imaging by utilizing existing telecommunication infrastructure and anthropogenic noise sources. With dense sensors at several meters’ spacing, the unaliased wavefield can provide unprecedented details for fault zones. In this work, we use a DAS array converted from a 10-km underground fiber-optic cable across Ridgecrest City, California. We report clear spurious arrivals and coda waves in ambient noise cross-correlations caused by surface-to-surface wave scattering. We use these scattering-related waves to locate and characterize potential faults. The mapped fault locations are generally consistent with those in the USGS Quaternary Fault database of the United States but are more precise. We also use waveform modeling to infer that a 35-m wide, 90-m deep fault with 30% velocity reduction can best fit the observed scattered coda waves for one of the identified fault zones. These findings demonstrate the potential of DAS for passive imaging of fine-scale faults in an urban environment.