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AGU: Geophysical Research Letters

 

Keywords

  • resistivity structure
  • strain accumulation
  • seismogenic zone

Index Terms

  • Geomagnetism and Paleomagnetism: Geomagnetic induction
  • Geodesy and Gravity: Tectonic deformation
  • Seismology: Seismicity and tectonics
  • Structural Geology: Kinematics of crustal and mantle deformation
  • Seismology: Continental crust

Abstract

Magnetotelluric transect across the Niigata-Kobe Tectonic Zone, central Japan: A clear correlation between strain accumulation and resistivity structure

R. Yoshimura

DPRI, Kyoto University, Uji, Japan

N. Oshiman

DPRI, Kyoto University, Uji, Japan

M. Uyeshima

ERI, University of Tokyo, Tokyo, Japan

H. Toh

Department of Earth Sciences, University of Toyama, Toyama, Japan

T. Uto

DPRI, Kyoto University, Uji, Japan

H. Kanezaki

Department of Earth Sciences, University of Toyama, Toyama, Japan

Y. Mochido

Department of Civil Engineering, Tottori University, Tottori, Japan

K. Aizawa

ERI, University of Tokyo, Tokyo, Japan

Y. Ogawa

VFRC, Tokyo Institute of Technology, Tokyo, Japan

T. Nishitani

Department of Earth Science and Technology, Akita University, Akita, Japan

S. Sakanaka

Department of Earth Science and Technology, Akita University, Akita, Japan

M. Mishina

RCPEVE, Tohoku University, Sendai, Japan

H. Satoh

AIST, Tsukuba, Japan

T. Goto

JAMSTEC, Yokosuka, Japan

T. Kasaya

JAMSTEC, Yokosuka, Japan

S. Yamaguchi

Department of Earth and Planetary Sciences, Kobe University, Kobe, Japan

H. Murakami

Department of Applied Science, Kochi University, Kochi, Japan

T. Mogi

ISV, Hokkaido University, Sapporo, Japan

Y. Yamaya

ISV, Hokkaido University, Sapporo, Japan

M. Harada

EPRC, Tokai University, Shizuoka, Japan

I. Shiozaki

Department of Civil Engineering, Tottori University, Tottori, Japan

Y. Honkura

Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo, Japan

S. Koyama

ERI, University of Tokyo, Tokyo, Japan

S. Nakao

DPRI, Kyoto University, Uji, Japan

Y. Wada

DPRI, Kyoto University, Uji, Japan

Y. Fujita

DPRI, Kyoto University, Uji, Japan

We obtained an electrical transect image of the Niigata-Kobe Tectonic Zone (NKTZ). Several major active faults are located in this zone of concentrated deformation. The main features of the final two-dimensional model are a thick resistive block in the upper crust, with a thinned-out portion beneath the Atotsugawa Fault, and a strong conductor in the lower crust that intrudes upward into the upper resistor. The upper crustal resistive zone corresponds well to the spatiality of the NKTZ, and relatively conductive zones sandwiching this resistor may contribute to observed changes in displacement rates. The overlapping locations of the conductor and the low-velocity body in the lower crust indicate that the conductor represents a zone that was weakened by fluids. Given that microearthquakes are localized in the regions between the resistive and conductive zones, we suggest that the distribution of earthquakes is influenced by intrusions of fluid derived from the conductor.

Received 16 July 2009; accepted 15 September 2009; published 23 October 2009.

Citation: Yoshimura, R., et al. (2009), Magnetotelluric transect across the Niigata-Kobe Tectonic Zone, central Japan: A clear correlation between strain accumulation and resistivity structure, Geophys. Res. Lett., 36, L20311, doi:10.1029/2009GL040016.

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