Construction and Field-Testing of 16 Broadband Ocean Bottom Seismographs for the OBSIC Fleet

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Understanding Earth processes, such as mantle dynamics and plate tectonics, and the phenomena they produce, such as earthquakes, volcanoes, and planet-scale elemental cycling, requires sustained deployments of seafloor instruments, since ~ 70% of the earth's surface is covered by the oceans. While data from land-based instruments can tell us much about large-scale structure and earthquake activity under the oceans, many questions related to the structure and dynamics of mid-ocean ridges, hot-spots, subduction zones, and continental margins can only be addressed by data acquired with Ocean Bottom Seismometers (OBSs). Discovery is advanced by an efficient, effective means for scientists to acquire ocean-bottom seismic data. The Ocean Bottom Seismometer Instrument Center (OBSIC) at Woods Hole Oceanographic Institution (WHOI) provides seafloor seismographs and at-sea technical support to all U.S. investigators whose research would benefit from seafloor seismic observations. OBSIC currently operates a fleet of 124 Ocean-Bottom Seismographs (OBS), of which 30 are short-period and the remaining 94 are broadband units of varied type. This award support construction of 16 new broadband ocean-bottom seismographs that will bring the total OBSIC fleet to 150 and the broadband OBS count to 110. The new OBS will carry a Nanometrics Trillium T-240 3-component broadband seismometer and a Differential Pressure Gauge, be deployable to 6000 m, and have an endurance of at least 15 months. The OBS will be equipped with a low-powered Seascan clock disciplined by a power-cycled Chip-Scale Atomic Clock that will provide improved timing accuracy without an undue power penalty. Overall, these new instruments are an important enhancement to the NSF-supported OBS fleet, and will increase OSBIC's capacity to field OBS arrays with greater numbers of instruments, to support additional contemporaneous experiments, and to reduce the wait-time for the deployment of funded experiments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.