The top-to-bottom structure of the Garlock Fault Zone uncovered with fiber sensing

James W. Atterholt, Zhongwen Zhan, Yan Yang, & Weiqiang Zhu

Submitted September 10, 2023, SCEC Contribution #13072, 2023 SCEC Annual Meeting Poster #051

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 image the near surface using surface wave observations from an active source experiment and ambient noise cross correlations. We subsequently probe the shallow crust using travel-times from a cluster of earthquakes that ruptured near the fault. Finally, we use differential travel times from many earthquakes to localize the structure at seismogenic depths. We find that the fault’s low-velocity zone is confined to the top few-hundred meters and that there is a sharp bimaterial contrast at depth, with the south side having a higher velocity. These findings suggest significant fault zone healing and a preferred westward rupture directivity.

Key Words
Garlock Fault, Distributed Acoustic Sensing, Fault Zone Imaging

Citation
Atterholt, J. W., Zhan, Z., Yang, Y., & Zhu, W. (2023, 09). The top-to-bottom structure of the Garlock Fault Zone uncovered with fiber sensing. Poster Presentation at 2023 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology