Seafloor Subsidence Associated With Plate Convergence Detected by Long‐Term Pressure Recordings in the Nankai Trough, Japan

Vertical‐component seafloor deformation reflects the state of plate couplings in the seismogenic zone, and measuring long‐term seafloor displacements is possible over time using seafloor pressure gauges. However, difficulties remain in estimating the vertical displacements from pressure gauges owing to the sensor drift of pressure gauges. Therefore, in situ pressure calibrations were conducted repeatedly at two seafloor observatories using a mobile pressure calibrator, and the inherent drift was corrected. Here, drift‐corrected long‐term pressure recordings from two seafloor observatories were presented in the Nankai Trough, Japan. The results suggest that the static subsidence is exhibited at the two observatories. These observations are comparable to those in existing literature based on plate convergence modeling and support other geodetic observations in this region. This is the first quantitative observation of small and long‐term seafloor subsidence associated with plate convergence in a seismogenic zone.