[S-IT40_1AM1] 地殻流体：その分布と変動現象への役割

[SIT40-01] 広帯域MT法による地殻内流体の3次元分布解明

*小川 康雄¹、市來 雅啓²、神田 径¹ (1.東京工業大学火山流体研究センター、2.東北大学大学院理学研究科)

キーワード：地殻流体, マグネトテルリクス, 比抵抗, 3次元構造

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.