Deep structure of the ou mountain range strain concentration zone and the focal area of the 2008 Iwate-Miyagi Nairiku earthquake, NE Japan-seismogenesis related with magma and crustal fluid

The 2008 Iwate-Miyagi Nairiku earthquake (M 7.2) occurred on June 14, 2008 in a zone of concentrated deformation along the mountain backbone of Tohoku encompassing SW Iwate and NW Miyagi Prefectures, NE Japan. This earthquake was a shallow intraplate earthquake with the reverse-type focal mechanism. Regular seismic activity is high in this concentrated deformation zone. We have performed regional-scale seismic tomography in and around the focal area and found that the distinct low-velocity regions are continuously distributed from the mantle wedge to the lower crust just below the focal area and active seismic zones. This low-velocity zone can be interpreted to be a region of partial melting, suggesting that crustal fluids separating and upwelling from deeper portion may be closely related with the occurrence of both the active seismic zones and the 2008 earthquake.