The break of earthquake asperities imaged by distributed acoustic sensing.

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 networks 12 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.