Abstract
On-land ophiolites (crust-mantle fragment of a fore-arc lithosphere) and high-pressure metamorphic belts (deeply subducted and later up-heaved accretionary complex) are comparable in size to the aftershock focal areas of M9.0 mega-earthquakes such as 2011 Tohoku Earthquake in Japan, and are exposed as continuous geological bodies bounded by thrust faults. The association of ophiolites and high-pressure metamorphic belts are reported not only from on-land orogenic belts but also from sea floor of the Izu-Mariana fore-arc at a current subduction zone. The 2011 Tohoku Earthquake (M9.0) caused more than 25 m thrust movement along the fault that extends from the trench to more than 100 km depth. If the up-thrust movement like this repeatedly happens every 1,000 years, then the high-pressure metamorphic rocks may be transported to the surface within 4 million years. The wide exposures of 4 Ma ophiolite and high-pressure metamorphic rocks are actually reported from Indonesia. These geological facts suggest that the up-thrusting movement of the ophiolites and high-pressure metamorphic rock may be the geological actuality of the mega-earthquakes in subduction zones.
