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-SS 地震学

[S-SS04] [EE] Subduction zone dynamics from regular earthquakes through slow earthquakes to creep

2017年5月24日(水) 17:15 〜 18:30 ポスター会場 (国際展示場 7ホール)

[SSS04-P02] 3-D resistivity distribution around an intra-plate slow earthquake area in northern Hokkaido, Japan: relationship between serpentine and slow earthquake

*市原 寛1茂木 透2内田 利弘3山谷 祐介3多田 訓子4 (1.神戸大学、2.北海道大学、3.産業総合研究所、4.海洋研究開発機構)

A slow earthquake of Mw 5.4 is estimated in the Dohoku area, northern Hokkaido Island (Ohzono et al., 2015). Because most of slow earthquakes have been reported in the vicinity of plate boundaries, study of the intra-plate events is important to understand the slow earthquakes. In this study, we estimated a resistivity distribution based on the 3-D inversion of magnetotelluric (MT) data at 45 sites in the Dohoku area. The inverted resistivity model shows the following features. 1) A surface conductive layer is distributed in the most part of the study area. The thickness of the conductor increases toward westward and reaches approximately 5 km at the Japan Sea side. The conductive layer is interpreted as Tertiary-Quaternary sedimentary rocks. 2) An ultra-conductive area (0.1-10 ohm-m, 0-10 km depth) is distributed around the fault of the slow earthquakes. Based on the surface geological distribution and magnetic anomaly (GSJ, 2005), the conductor possibly reflects serpentine-related geological unit associated with the slow slip events. However, a careful interpretation is required because a serpentinite sampled from a few ten meters depth at about 10 km south of the study area is not so conductive (10-100 ohm-m) (Okazaki et al., 2011). This possibly indicates that conductive fluid from deep earth fills pores of serpentine and decreased resistivity.