[S-SS03] Seismological advances in the ocean

[SSS03-02] Global Seismology from Within the Oceans: Exploring the MERMAID Data Set Being Actively Recorded in the South Pacific

★Invited Papers

*Joel D. Simon¹, Frederik J. Simons¹, Jessica C. E. Irving², The EarthScope-Oceans Consortium - (1.Department of Geosciences, Princeton University, 2.School of Earth Sciences, University of Bristol)

Keywords:MERMAID, South Pacific Ocean, Seismoacoustics , Seismic Tomography

Mobile Earthquake Recording in Marine Areas by Independent Divers, MERMAIDs, are robotic floats that autonomously detect and transmit records of global seismicity from within the oceans. Their main objective is the recording of ~1 Hz teleseismic P waves of tomographic quality sampling novel raypaths through the mantle. MERMAID is not an ocean-bottom seismometer but rather a floating hydrophone equipped with GPS, two-way Iridium communication for data upload and download, and a hydraulic pump allowing it to be neutrally buoyant at depths ranging from the sea surface to 2000 m. Data are recorded while drifting with mid-column ocean currents, generally at a depth of 1500 m, over repeated dive cycles. Signals deemed by the onboard detection algorithm to be most promising are automatically sent to us in near real-time in roughly four-minute data segments, while longer segments remain retrievable from the one-year buffer via two-way Iridium communication. In 2018 the international EarthScope-Oceans Consortium began deploying a large MERMAID array around French Polynesia as part of the South Pacific Plume Imaging and Modeling Project with the goal of refining tomographic models of the area using MERMAID data. Here we report on the current data set---nearly 4000 data segments as of early 2022 with more being sent daily---amassed by 16 of those MERMAIDs maintained by Princeton University. We show that these signals are of sufficient quality for high-resolution tomographic inversion and give an early indication of what sort of structures they may ultimately reveal. We also showcase seismoacoustic signals beyond the P mantle wave, including conversions of S and Rayleigh waves, and core phases recorded by our floats, proving that MERMAID data are useful for more than just P-wave tomography. Finally, we introduce the publicly available MERMAID data set archived with the IRIS DMC, and briefly touch on new metadata standards developed to track our moving stations.