Dense AMT Observations Across the Japan Median Tectonic Line Izumi Fault Zone
大内, 悠平 ,
吉村, 令慧 ,
田中, 大資 ,
米田, 格山崎, 友也
京都大学防災研究所年報. B = Disaster Prevention Research Institute Annuals. B
65 , 2015-06 , 京都大学防災研究所
The Japan Median Tectonic Line Fault Zone (MTL) is a fault system that extends for about 360km and locates along the geological boundary between the Ryoke and the Sanbagawa belts. Izumi segment fault zone of MTL consists of Gojyodani and Shobudani faults, etc. Wideband MT soundings were carried out across these faults (DPRI, Kyoto Univ., 2014). The obtained resistivity model was characterized by a contrast around MTL. However, the shallow resistivity structure was not so clear. In order to delineate fine subsurface electrical structure of the fault, we carried out audio-frequency magnetotellurics (AMT) measurements at 38 sites along a 5km profile across the Gojyodani and Shobudani faults in November 2014. As the result of remote reference processing using local and far remote sites, we obtained superior quality MT responses at almost all of the AMT sites. Pseudo-sections of responses, phase tensor ellipses and induction vectors indicate that there are several characteristic features beneath faults.