Geo-Sense: a portable distributed acoustic sensing (DAS) system for high-resolution seafloor monitoring.

Distributed fiber-optic sensing remains underutilized in seafloor geomorphic research, in part because global submarine cable networks are typically located far from areas of primary scientific interest. Here we present Geo-Sense, a portable, autonomous Distributed Acoustic Sensing (DAS) system designed for rapid, targeted deployment and high-resolution seafloor monitoring without reliance on permanent telecommunications infrastructure. The system integrates a low-power interrogator, battery power, and a 1 km steel-armored sensing cable. Performance was evaluated during an eight-day deployment at 380 m water depth in Monterey Bay, California, using well-characterized seismic and oceanographic signals as benchmarks. Geo-Sense identified all cataloged earthquakes during the deployment and recorded additional uncataloged seismic and hydroacoustic events. DAS-derived magnitudes show strong agreement with catalog values, and source-receiver distance estimates derived from P-S arrival times are consistent with catalog-reported distances. Beyond seismicity, broadband DAS amplitude (4-30 Hz) exhibits multi-hour modulation correlated with near-bottom current velocities, while lower-frequency wave and microseism bands display coherent tidal modulation. Signal quality is strongly influenced by cable-seafloor coupling and geometry. These results demonstrate that portable DAS systems can provide spatially distributed observations of both microseismicity and tidally driven processes in submarine canyon environments.