HR: 0830h
AN: S11F-0361    [PDF]
TI: Usage of Fractal Model of Elastic and Electrical Properties of Porous Rock for Recognition of Liquid-Saturated Pore Zones From Collocated Seismic and Magnetotelluric Experiments: Deep Extension of Nagamachi-Rifu Fault Case
AU: * Ito, H
EM: hisao.itou@aist.go.jp
AF: National Institute of Advanced Industrial Science and Technology (AIST), Geological Survey of Japan (GSJ), Central 7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan
AU: Pervukhina, M
EM: marina-pervuhkina@aist.go.jp
AF: National Institute of Advanced Industrial Science and Technology (AIST), Geological Survey of Japan (GSJ), Central 7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan
AU: Kawahara, Y
EM: y-kuwahara@aist.go.jp
AF: National Institute of Advanced Industrial Science and Technology (AIST), Geological Survey of Japan (GSJ), Central 7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan
AB: A theoretical model was involved for quantitative joint analysis of collocated seismic velocity tomography and electromagnetic experiments. The main advantage of the present model against other theoretical models is possibility to describe both elastic and electrical properties of rock with a single model for a wide range of microstructures including 3D grain and pore anisotropy and different interconnection extend from isolated to interconnected pores. Based on the developed model, an attempt have been made to elaborate a quantitative method for solving the problem whether the variation of resistivity and seismic velocities in a region can be attributed to presence of liquid only or whether another assumption should be involved. The suggested method was applied for analyzing a collocated seismic velocity tomography and MT experiment carried out across the active Nagamachi-Rifu fault running through Sendai city, Northeastern Japan. Several zones, where the perturbation of both velocity and resistivity can be explained with several percentage of liquid fraction, were recognized in the region, namely, a caldera and a deep extension of the Nagamachi-Rifu fault. In the caldera region at the shallow depth of 3 km, the reduction of the seismic velocities up to 10% and the low resistivity about several ohm_~m were explained by about 3% of porosity. At the depth of 15 km a zone of the low velocity of 5-10% decrease and of the low resistivity about tens of ohm_~m were explained by about 2% of porosity and interpreted as the deep extension of the Nagamachi-Rifu fault. The developed model allows involving in quantitative analysis of 3 independent parameters: compressional and shear velocities and resistivity and can be used for parameterization of a joint MT and seismic inverse problem in a variety of geological settings.
DE: 0925 Magnetic and electrical methods
DE: 3210 Modeling
DE: 7203 Body wave propagation
DE: 8010 Fractures and faults
SC: Seismology [S]
MN: 2003 Fall Meeting