[S-EM14] Electric, magnetic and electromagnetic survey technologies and scientific achievements

[SEM14-19] Anisotropic electrical conductivities of cracked rocks filled with conductive material

*Yoshiya Usui¹ (1.Earthquake Research Institute, the University of Tokyo)

Keywords:anisotropy, electrical resistivity, mixing model, crack

It is believed that subsurface electrical conductivities have more or less anisotropy. For example, fluid-filled cracks, fractures, and faults will make the electric current flow preferably to a direction (e.g., along the direction parallel to cracks). Anisotropic conductivity structure has been estimated in some places where strong anisotropy was expected. To interpret the conductivity structure estimated by the electromagnetic survey, the mixing model, which gives bulk electrical conductivity of rocks, is a crucial factor. Although varieties of mixing models have been proposed, most models are tended for the isotropic conductivity structure. Thus, this study develops a mixing model considering the transverse anisotropy of the orientation of fluid-filled cracks based on the statistical method of Gueguen & Dienes (1989). The author derived the model assuming that the probability of the normal vectors of cracks follows the Watson distribution. The developed mixing model can be used to interpret anisotropic conductivity structures and to give constraints on the inversion considering anisotropic conductivity.