Collaborative Research: Permanent seafloor benchmarks for geodetic measurements of horizontal and vertical plate motion

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The PI's request funding to increase the longevity of seafloor geodetic measurements by developing and demonstrating an inexpensive, permanent seafloor benchmark. The benchmark will provide a physical tie to the sea floor lasting for decades (perhaps longer) on which geodetic sensors can be repeatedly placed and removed with millimeter resolution. Global coordinates estimated with seafloor geodetic techniques will remain attached to the benchmark allowing for the interchange of sensors as they fail or become obsolete, or for the sensors to be removed and used elsewhere, all the while maintaining a coherent series of positions referenced to the benchmark. The benchmark will be designed to be lowered via a wire to the seafloor with sensors attached. The sensors will be capable of being recalled via an acoustic command sent from a ship to release from the benchmark and freely float to the sea surface for recovery. The duration of the sensor attachment to the benchmark will last from a few days to a few years depending on the specific needs of the experiment. The recovered sensors are then available to be reused at other locations, or again at the same site in the future.Broader Impacts:If high accuracy, cheap, campaign-style seafloor geodesy can be developed, the studies that could be done with such a system could transform our knowledge of subduction zones and megathrust earthquakes.