JpGU-AGU Joint Meeting 2017

講演情報

[EE]Eveningポスター発表

セッション記号 S (固体地球科学) » S-CG 固体地球科学複合領域・一般

[S-CG62] [EE] 変動帯ダイナミクス

2017年5月23日(火) 17:15 〜 18:30 ポスター会場 (国際展示場 7ホール)

[SCG62-P31] 紀伊半島のMT法による3次元地殻流体分布

*木下 雄介1小川 康雄1齋藤 全史郎1野口 里奈1藤田 清士2山口 覚3梅田 浩司4浅森 浩一5市來 雅啓6 (1.東京工業大学、2.大阪大学、3.大阪市立大学、4.弘前大学、5.日本原子力研究開発機構、6.東北大学)

Although Kii peninsula is located in the forearc side of southwest Japan, it has high temperature hot springs and fluids from mantle are inferred from the isotopic ratio of helium. Non-volcanic tremors underneath the Kii Peninsula suggest rising fluids from slab.
Previously, in the southern part of the Kii Peninsula, wide band magnetotelluric measurements were carried out (Fujita et al. ,1997; Umeda et al. ,2004). These studies could image the existence of the conductivity anomaly in the shallow crust and in the deep crust. Long period observation using network MT data showed low resistivity on wedge mantle(Yamaguchi et al., 2009). These studies, however, used two dimensional inversions and three-dimensionality is not fully taken into consideration.
As part of the “Crustal Dynamics” project, we have measured 20 more stations so that the whole wide-band MT stations constitute grids to make three-dimensional modeling of the area.

In total we have wide-band magnetotelluric sites. Preliminary 3d inverse modeling showed the following features.
(1) The high resistivity in the eastern Kii Peninsula at depths of 5-40km. This may imply consolidated magma body of Kumano Acidic rocks underlain by resistive Philippine Sea Plate which subducts with a low dip angle.
(2) The northwestern part of Kii Peninsula has the shallow low resistivity in the upper crust.
(3) The northwestern part of the survey area has a deeper conductor in the lower crust to upper mantle.This reflects the Phillipine Sea subduction with higher dip angle.