Fault Zone Imaging With Distributed Acoustic Sensing: Body‐To‐Surface Wave Scattering

Fault zone structures at many scales largely dictate earthquake ruptures and are controlled by the geologic setting slip history. Characterizations of these diverse inform better understandings hazards phenomenology. However, characterizing fault zones sub-kilometer has historically been challenging, challenges exacerbated in urban areas, where locating faults is critical for hazard assessment. We present a new procedure using distributed acoustic sensing (DAS). This technique involves backprojection DAS-measured scattered wavefield generated natural earthquakes. framework provides measure strength scattering along DAS array thus constrains positions properties local scatterers. The high spatial sampling arrays makes possible resolution scatterers scale tens meters over distances kilometers. test this methodology Ridgecrest, CA which recorded much 2019 Mw7.1 Ridgecrest aftershock sequence. show that peaks spatially correlated with mapped region frequency-dependent. model as shallow, low-velocity consistent how we may expect to perturb velocity structure. geometry can be constrained comparing our observations synthetic tests.