SEA‑SEIS ocean bottom seismometer network in the Northeast Atlantic: Performance, data properties, biological observations and audification innovations

Project SEA-SEIS deployed 18 ocean-bottom seismometers (OBS) in the northeast Atlantic Ocean, between Ireland and Britain in the east and Iceland and the Mid-Atlantic Ridge in the northwest. The 3-component, broadband instruments, each with an additional broadband hydrophone, were deployed for 19 months, from September-October, 2018, to April-May, 2020. A key goal of the deployment was to advance our understanding of the structure and dynamics of the North Atlantic lithosphere and underlying mantle, origins of the North Atlantic Igneous Province and the morphology of the Iceland Plume. Fourteen of the 18 instruments were retrieved, with 2 of the 14 showing problems with the data that limited their use. The remaining 12 OBSs provided continuous, 19-month recordings from across a large part of the North Atlantic seafloor. As observed elsewhere, the OBS noise level is higher than at land stations, due to the poorer coupling to the surface and noise from ocean currents and waves. Data pre-processing comprised the clock-drift correction, horizontal-component-orientation determination and compliance- and tilt-noise suppression. Every seismometer came up with multiple sea-creature species attached to it, bringing useful information on their habitats. At depths up to ~1200 m, octopuses used the OBSs to lay and guard their eggs. In addition to conventional processing, seismic data was also transformed to audible frequency ranges. New methods for translating the data’s spatial information to ambisonic surround sound were developed. The audifications offered a new perspective on the data and underpinned a productive art-science collaboration and an outreach program.