Seismic imaging of solid/fluid structure below and ocean vertical mixing structure above the seafloor

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In an attempt to apply seismic exploration data acquired for submarine crustal structures to imaging of ocean acoustic structure, we obtained the following results. 1.Very-low-frequency earthquakes occurring in the Nankai accretionary prism represent very slow plate-boundary slip as well as hydrofractures involving fluid migration through the plate boundary. 2.We proposed several methods to obtain improved images of ocean structure from seismic exploration data. 3.We analyzed data from off Hokkaido, off Izu-Bonin ridge to detect signals of the Kuroshio warm core rings, M2 internal tides and the Kuroshio front. 4.A detailed analysis was made for the M2 internal tides to find evidence of billows and critical layer absorption. 5.We made a numerical simulation of internal tidal waves interacting with the background field of internal gravity waves to estimate their dissipation rate.