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Vertical crustal movement on the seafloor detected with differential pressure monitoring

We have developed ocean bottom pressure meters (OBPs) with quartz pressure sensors. After several times of seafloor observation with two OBPs, we have confirmed that the drift rate of each pressure sensor is constant, and that differential pressure monitoring fairly well cancels not only tidal variations but effects of intermediate-term ocean dynamics. We applied this method to an earthquake swarm event 2000 near Miyake Island, Japan. The result indicated subsidence of the seafloor in the center of the swarm by 6 cm/15 days relative to the surrounding area. The estimation agrees with observed results at tidal stations as well as the source mechanism of the earthquakes.