DI13A-2632
A Mantle Wedge Flow Model as Revealed by Three-dimensional Electrical Resistivity Image beneath Northeastern Japan
Monday, 14 December 2015
Poster Hall (Moscone South)
Masahiro Ichiki1, Yasuo Ogawa2, Toshiki Kaida1, Tomotsugu Demachi1, Satoshi Hirahara1, Yoshimori Honkura2, Hiroshi Ichihara3, Wataru Kanda2, Toshio Kono1, Takao Koyama4, Masaki Matsushima2, Takashi Nakayama1, Syuichi Suzuki1, Hiroaki Toh5 and Makoto Uyeshima6, (1)Tohoku University, Sendai, Japan, (2)Tokyo Institute of Technology, Tokyo, Japan, (3)JAMSTEC, Yokosuka, Japan, (4)Earthquake Research Institute, University of Tokyo, Tokyo, Japan, (5)Kyoto University, Kyoto, Japan, (6)Earthquake Research Institute, Tokyo, Japan
Abstract:
We conducted long-period magnetotelluric observations in northeastern Japan from 2010 to 2013 to investigate the three-dimensional electrical resistivity distribution of the subduction zone. Incorporating prior information of the subducting slab into the inversion scheme, we obtained a three-dimensional resistivity model in which a vertically continuous conductive zone is imaged from the subducting slab surface to the lower crust beneath the the central orogenic belt of the northeastern Japan arc (Ou Backbone Range). The conductive body indicates a saline fluid and/or melt pathway from the subducting slab surface to the lower crust. The lower crust conductor is 10 Ωm or more conductive, and the estimation of saline fluid and/or melt volume fraction is 0.7 vol. % at minimum. Other resistivity profiles in the across-arc direction reveal that the conductive body segregates from the subducting slab surface at 80–100 km depth and takes an overturned form toward the backarc direction. The head of the conducting body reaches the lower crust just beneath Mt. Gassan, one of the prominent backarc volcanoes. This suggests that the backarc volcanism is caused by saline fluid and/or melt overturn rising toward the backarc direction.
