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

[SSS04-P40] Large-scale electrical resistivity structure around the long-term Slow Slip Events beneath the Bungo Channel region, southwest Japan

*吉村 令慧¹、山崎 健一¹、小川 康雄²、中川 潤¹、川崎 慎吾¹、小松 信太郎¹、米田 格¹、大内 悠平³、岡崎 智久³、鈴木 惇史⁴、齋藤 全史郎⁴、臼井 嘉哉⁴、寺石 眞弘¹ (1.京都大学防災研究所、2.東京工業大学理学院火山流体研究センター、3.京都大学大学院理学研究科、4.東京工業大学理工学研究科)

キーワード：slow slip events, Bungo Channel, resistivity structure

Recent geodetic observations detect recurrent slow slip events (SSEs), which occurred beneath the Bungo Channel and southwest Shikoku Island, with interval of approximately 6 years (e.g. GSI, 2010). In order to reveal a large-scale three-dimensional resistivity structure around SSEs region, we carried out wideband magnetotelluric (MT) surveys around the western part of Shikoku Island. We also plan to establish a permanent long-term MT monitoring network that aims to detect temporal changes of resistivity structure during SSE cycle. As of June, 2016, MT surveys were performed at 31 sites by using Phoenix wideband MT instruments. In the most of sites, high quality MT responses were obtained using the BIRRP code (Chave and Thomson, 2004) for the period range 300 Hz to 10,000 sec. The spatial distributions of the phase tensor ellipses and the induction vectors suggest that resistivity contrasts are located surrounding SSEs. In this presentation, we show the results of the data analysis and preliminary inverted three-dimensional model around the transition zone between SSEs and stick-slip regions.