Assessing the Earthquake Recording Capability of an Ocean-Bottom Distributed Acoustic Sensing Array in the Sanriku Region, Japan

Abstract Sparse seismic instrumentation in oceans limits our understanding of the Earth’s dynamics. The emerging technology of distributed acoustic sensing (DAS), which can turn existing fiber-optic cable arrays into thousands of seismic sensors, has the potential to fill the data gap. Yet, the power of ocean-bottom DAS (OBDAS) for routine seismic monitoring has to be further explored. In this study, we investigate the recording capability of an OBDAS array in the Sanriku region, Japan. We first compare the manually selected OBDAS records with a collocated ocean-bottom seismometer (OBS) and demonstrate that OBDAS can record high-fidelity earthquake waveforms when the power of earthquake signals exceeds the OBDAS noise level. We then propose two array-based detection methods, that is, waveform similarity search and spectrum similarity search, to detect coherent signals across the OBDAS array. With these algorithms, we successfully detect ≈80% of cataloged earthquakes within a 100 km radius region as well as thousands of previously uncataloged local events. At the same time, we also show that the quantity and quality of recorded earthquake waveforms vary substantially across OBDAS channels. Our results reveal the promising potential of OBDAS as a tool to complement the current sparse underwater seismic network for studies in observational seismology.