3D imaging of geofluid by wideband magnetotellurics

Yasuo OGAWA; Masahiro ICHIKI; Wataru KANDA

Presentation information

Oral

Symbol S (Solid Earth Sciences) » S-IT Science of the Earth's Interior & Techtonophysics

[S-IT40_1AM1] Geofluids: their distribution and role in the Earth's dynamics

Thu. May 1, 2014 9:15 AM - 10:45 AM 416 (4F)

Convener:*Michihiko Nakamura(Division of Earth and Planetary Materials Science, Department of Earth Science, Graduate School of Science, Tohoku University), Hiroshi Sakuma(Department of Earth and Planetary Sciences, Graduate School of Science and Engineering, Tokyo Institute of Technology), Masahiro Ichiki(Graduate School of Science, Tohoku University), Tsutomu Takahashi(Institute for Research on Earth Evolution Japan Agency for Marine-Earth Science and Technology), Chair:Masahiro Ichiki(Graduate School of Science, Tohoku University), Hiroshi Sakuma(National Institute for Materials Science)

9:15 AM - 9:30 AM

[SIT40-01] 3D imaging of geofluid by wideband magnetotellurics

*Yasuo OGAWA¹, Masahiro ICHIKI², Wataru KANDA¹ (1.Volcanic Fluid Research Center, Tokyo Institute of Technology, 2.Graduate School of Science, Tohoku University)

Keywords:geofluid, magnetotellurics, resistivity, 3d

Magnetotelluric measurements have been conducted over the five years in the central part of NE Japan arc surrounding the Naruko Volcano with approximately 3km grid. Over 200 sites were used for modeling the crustal resistivity structure in detail. Full impedance tensors for 8 periods were used for inversion. To alluviate the computational load, first four short periods were used to image upper crustal features and the resultant model was used for a prior model for another set of inversions with longer 4 periods.The obtained model show the crustal conductor underneath the Mukaimachi caldera and Sanzugawa caldera. Seismic tomography shows low S-wave velocity for both, however, the resistivity image show clear low resistivity for Mukaimachi Caldera, but not for Sanzugawa Caldera. This difference may be due to the salinity of the fluids underlying the volcanic regions.