Aftershocks of the Ridgecrest earthquake sequence on four dense fiber seismic arrays

Ethan F. Williams, Zhongwen Zhan, Zefeng Li, Martin Karrenbach, Thomas Coleman, Lisa LaFlame, Steve Cole, & Victor Yarsev

Published August 13, 2019, SCEC Contribution #9502, 2019 SCEC Annual Meeting Poster #240

Recent advances with distributed acoustic sensing (DAS) have demonstrated the ability of pre-existing telecommunications cables to be repurposed as dense arrays of linear strainmeters, effective for scalable seismic monitoring. The extensive fiber networks throughout Southern California have provided a unique opportunity to record the thousands of aftershocks produced by the 2019 Ridgecrest earthquake sequence through rapid deployment of four DAS arrays. Following the mainshocks in early July, the Caltech Seismological Laboratory partnered with the California Broadband Cooperative to establish three temporary DAS networks along U.S. Route 395, to the west of the rupture. Two arrays north and south of Olancha and one array west of Ridgecrest illuminate 30 km of cable. A fourth array was subsequently deployed along a 20-km fiber at the Jet Propulsion Laboratory’s Goldstone Deep Space Communications Complex in the central Mojave. Together, these networks encircle the area of continued seismic activity with over 6,000 continuously recording channels.

In this poster, we show examples of aftershocks recorded on the four fiber seismic arrays. With a channel spacing of only 2-8 m, observed earthquake wavefields exhibit tremendous complexity. In addition to the expected P, S, and surface wave phases, we find scattered waves, mode conversion associated with local micro-basins, and numerous refracted arrivals presumably associated with basin edge effects. This rich dataset offers the potential for earthquake detection and relocation, array-based imaging of regional geologic structure, and ground motion validation across a broad region, among numerous applications. We demonstrate that pop-up DAS arrays are an efficient approach to rapid response instrumental deployment and should be incorporated by the Southern California earthquake science community into future event response planning.

Key Words
Ridgecrest, DAS

Citation
Williams, E. F., Zhan, Z., Li, Z., Karrenbach, M., Coleman, T., LaFlame, L., Cole, S., & Yarsev, V. (2019, 08). Aftershocks of the Ridgecrest earthquake sequence on four dense fiber seismic arrays. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Ridgecrest Earthquakes