Delineation of a fault zone using high-density array CSAMT method

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We conducted a high-density arrayed CSAMT survey to delineate active fault in the eastern foot of Tsugaru Mountains in Japan. The survey purpose is to delineate subsurface structure of this area including blind thrust as materials of predicting the magnitude of an earth quake. In this area, the seismic reflection survey was conducted. The CSAMT survey line was a part of seismic survey line and the length was 4.6 km. We set 93 scalar measurement stations at intervals of 50 m so as to be able to capture steep structures. We used Geode EM3D as receivers and GeoTx20 as a transmitter, manufactured by Geometrics. Geode EM3D receiver is multi-channel and distributed EM survey instruments. We set 6 receivers array at maximum. Each receiver can collect 3 scalar measurements of adjacent stations. Hence we can acquire 18 stations during a procedure of transmitting 33 kinds of frequencies from 0.125 Hz to 8192 Hz. Such array CSAMT measurement contributed to improve measurement efficiency. The result of resistivity section clearly presents a gap of low resistivity zone. From integrated interpretation with seismic reflection, we concluded that the gap of low resistivity structure seems to be caused by blind thrust. Presentation Date: Wednesday, September 27, 2017 Start Time: 3:55 PM Location: Exhibit Hall C, E-P Station 2 Presentation Type: EPOSTER