南海トラフ
The Nankai Trough area was identified by the United States Department of Energy (DOE) and its United States Department of Energy National Laboratories (NETL) as an important hydrate-bearing region in the Asian-Pacific. DOE gas hydrate resource estimates indicate a hydrate potential of 16 to 27 trillion cubic meters. Research has confirmed the presence of gas hydrates in two different locations within the Nankai Trough: the hydrates can be found in the accretionary prism off Shikoku and Tokai, and also in the back-arc basin system northwest of Japan. Nearly all of the natural gas hydrate accumulations identified in the Nankai Trough region occur at a depth of around 290 to 300 meters below the seafloor (1,240 meters below sea-level).