[S-EM12] Electric, magnetic and electromagnetic survey technologies and scientific achievements

[SEM12-P21] Re-analysis of broad-band magneto-telluric data in the focal region of the 2000 Western Tottori Earthquake

*Kensuke Nakamura¹, Koki Aizawa², Koichi Asamori³, Naoto Oshiman, Ichiro Shiozaki⁴, The 2001 Research Group for Crustal Resistivity structure (1.Department of Earth and Planetary Sciences, Graduate school of Science, Kyushu University, 2.Institute of Seismology and Volcanology, Faculty of Sciences, Kyushu University, 3.Japan Atomic Energy Agency, 4.Graduate School of Engineering, Tottori University)

Keywords:Mageto-telluric, The 2000 Western Tottori Earthquake

We show the resistivity structure around the focal region of the 2000 Western Tottori Earthquake (M7.3). The purpose of this study is to investigate the relationship between the rupture of the mainshock and the resistivity structure, which was not discussed in the previous study. By using the broad-band MT data obtained at 52 sites, Umeda et al. 2011 imaged a deep conductive body in the middle crust to the upper mantle on the southwestern side of the mainshock rupture. Combined with high ³He/⁴He ratio of hot spring gas around the focal region, and the special relationship between a deep conductive body and deep low frequency earthquakes, they suggested that magmatic fluids contributed to the occurrence of the mainshock. However, Umeda et al. 2011 did not investigate the special relationship between the resistivity structure and the slip distribution. We note that other conductors were also imaged by Umeda et al. 2011 on the northern and southern parts of the rupture fault. These two conductors may be related with the termination of the mainshock rupture. Therefore, in this re-analysis, we have special attention to the shape and uniqueness of the conductors suggested by Umeda et al. 2011.
In addition to the 52 broad-band MT sites in Umeda et al. 2011, we used 12 broad-band MT sites obtained by Universities (The 2001 Research Group for Crustal Resistivity structure, Japan, 2001). In this study, we use full components of the impedance tensor and geomagnetic transfer functions to image preliminary 3-D resistivity structure, and investigate its relationship to the slip distribution of the mainshock and also occurrence of the aftershocks.

References

The 2001 Research Group for Crustal Resistivity structure (2002), Preliminary Report on the 2001 Wide-band Magneto-telluric Soundings of Deep Crustal resistivity Structure in and around the Focal area of the 2000 Tottori-ken Seibu Earthquake, Japan. Annuals of Disas. Prev. Res. Inst., Kyoto Univ. No. 45 B.
https://www.dpri.kyoto-u.ac.jp/nenpo/no45/45b0/a45b0p43.pdf

Umeda K., Asamori K., Negi T., Kusano T., (2011) A large intraplate earthquake triggered by latent magmatism. Journal Geophys. Res. 116, B01207.
https://doi.org/10.1029/2010JB007963