Observation of Seafloor Crustal Deformation at the Nankai Margin, Japan

We developed an observation system for measuring seafloor crustal deformation composed of precise acoustic ranging and kinematic positioning technique. The repeatability of the system is 3 cm in both horizontal components. We observed the coseismic crustal deformation caused by the two Ml class offshore earthquakes at the Kumano Bay, Japan. From the repeated observation at the Suruga Bay, we obtained the horizontal velocity field that is consistent to the vectors observed by the nationwide GPS observation network. The observation of seafloor crustal deformation can provide better information of seafloor crustal deformation associated with crustal activities, such as coseismic displacement and plate convergence.