On the potential of using Distributed Acoustic Sensing (DAS) to build teleseism based ocean-tomography network

Abstract

The sound from marine teleseisms rank among some of the loudest in Earth’s Oceans, typically radiated into the ocean near the epicenter and propagating across the entire ocean basin. Acoustic sensing on ocean observatories provide a critical path to better understand origins of these low-frequency sound waves known as T-phases, and structure of the ocean over the megameter propagation through the ocean. Of the emerging technologies implemented on these observatories, distributed acoustic sensing (DAS) has the potential to revolutionize marine seismoacoustics. DAS can be implemented on unused oceanic fibers on the continental slopes surrounding an ocean basin could readily enable a teleseism based ocean-tomography network with surprisingly little new infrastructure. In November 2021, a DAS system installed on two runs of fiber optic cable that connect to an ocean observatory measuring offshore volcanic activity, detected a few examples of teleseismic T-phases. Combined with other hydroacoustic ocean observatories in the Pacific Ocean, the T-phase origins are localized to bathymetric features over 100 km from the epicenter, an important consideration when utilizing these T-phases as sources of opportunity to study the ocean.