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Imaging the Garlock Fault Zone with a Fiber: A Limited Damage Zone and Hidden Bimaterial Contrast
  • +1
  • James Atterholt,
  • Zhongwen Zhan,
  • Yan Yang,
  • Weiqiang Zhu
James Atterholt
Seismological Laboratory, California Institute of Technology

Corresponding Author:[email protected]

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Zhongwen Zhan
Seismological Laboratory, California Institute of Technology
Yan Yang
Seismological Laboratory, California Institute of Technology
Weiqiang Zhu
Department of Earth and Planetary Science, University of California Berkeley, Seismological Laboratory, California Institute of Technology


The structure of fault zones and the ruptures they host are inextricably linked. Fault zones are narrow, which has made imaging their structure at seismogenic depths a persistent problem. Fiber-optic seismology allows for low-maintenance, long-term deployments of dense seismic arrays, which present new opportunities to address this problem. We use a fiber array that crosses the Garlock Fault to explore its structure. With a multifaceted imaging approach, we peel back the shallow structure around the fault to see how the fault changes with depth in the crust. We first generate a shallow velocity model across the fault with a joint inversion of active source and ambient noise data. Subsequently, we investigate the fault at deeper depths using travel-time observations from local earthquakes. By comparing the shallow velocity model and the earthquake travel-time observations, we find that the fault’s low-velocity zone below the top few hundred meters is at most remarkably narrow, potentially indicating fault zone healing. Using differential travel-time measurements from earthquake pairs, we resolve a sharp bimaterial contrast at depth that suggests preferred westward rupture directivity.
29 Apr 2024Submitted to ESS Open Archive
29 Apr 2024Published in ESS Open Archive