The break of earthquake asperities imaged by distributed acoustic sensing

Jiaxuan Li; Taeho Kim; Nadia Lapusta; Ettore Biondi; Zhongwen Zhan

doi:10.1038/s41586-023-06227-w

The break of earthquake asperities imaged by distributed acoustic sensing

Nature. 2023 Aug;620(7975):800-806. doi: 10.1038/s41586-023-06227-w. Epub 2023 Aug 2.

Authors

Jiaxuan Li¹, Taeho Kim², Nadia Lapusta^{3

2}, Ettore Biondi³, Zhongwen Zhan³

Affiliations

¹ Seismological Laboratory, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA. jxli@caltech.edu.
² Mechanical and Civil Engineering, Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, USA.
³ Seismological Laboratory, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA.

PMID: 37532935
DOI: 10.1038/s41586-023-06227-w

Abstract

Rupture imaging of megathrust earthquakes with global seismic arrays revealed frequency-dependent rupture signatures^1-4, but the role of high-frequency radiators remains unclear^3-5. Similar observations of the more abundant crustal earthquakes could provide critical constraints but are rare without ultradense local arrays^6,7. Here we use distributed acoustic sensing technology^8,9 to image the high-frequency earthquake rupture radiators. By converting a 100-kilometre dark-fibre cable into a 10,000-channel seismic array, we image four high-frequency subevents for the 2021 Antelope Valley, California, moment-magnitude 6.0 earthquake. After comparing our results with long-period moment-release^10,11 and dynamic rupture simulations, we suggest that the imaged subevents are due to the breaking of fault asperities-stronger spots or pins on the fault-that substantially modulate the overall rupture behaviour. An otherwise fading rupture propagation could be promoted by the breaking of fault asperities in a cascading sequence. This study highlights how we can use the extensive pre-existing fibre networks¹² as high-frequency seismic antennas to systematically investigate the rupture process of regional moderate-sized earthquakes. Coupled with dynamic rupture modelling, it could improve our understanding of earthquake rupture dynamics.