Resistivity structure to reveal the evaluation of seismic gap and shear zones: two cases from Atotsugawa Fault, Japan
and southern granulite terrain of India
Hsung-Hung Liang
Abstract
The central portion of Atotsugawa Fault in Japan with low seismicity regarded as a seismic gap may be interpreted as a locked segment. Magnetotelluric surveys were carried out to depict the resistivity structure around Atotsugawa Fault. The low resistivity along Atotsugawa Fault possibly due to the fluid in the fracture zone; the section with higher seismicity may have higher fluid in the fault zone than in the low seismicity zone.
The deep resistivity structure derived from the wide band magnetotelluric investigations also suggest that low resistivity features correspond to two major shear zones, namely MBSASZ and PCSZ, located in the southern granulite terrain of India, respectively. Similarly, our deep resistivity images show that the transition come along between these two major shear zones. The features of low resistive at depths in the vicinity of major shear zones may relate to the presence of fluids.
We conclude that the resistivity structure of these two major region have the transition zone in the middle segment and extremely different electrical response between two sides ,one with high resistivity and the other with low resistivity. Therefore, we claim that resistivity structures around active faults can be a good index for evaluation on fault activities and causes of seismic gaps.
Reference
Singh S.B., Stephen J., (2006). Deep resistivity sounding studies in detecting shear zones: A case study from the southern granulite terrain of India. J. of Asian Earth Sci., 28, 55–62.
Tada-nori, Yasuo Wada, Naoto Oshiman, Norihiko Sumitomo, (2005). Resistivity structure of a seismic gap along the Atotsugawa Fault, Japan. Physics of the Earth and Planetary Interiors, 148, 55–72.