Japan Geoscience Union Meeting 2015

Presentation information


Symbol S (Solid Earth Sciences) » S-SS Seismology

[S-SS30] Earthquake Source Processes and Physics of Earthquakes

Mon. May 25, 2015 2:15 PM - 4:00 PM A05 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Ryosuke Ando(Graduate School of Science, University of Tokyo), Yuko Kase(Active Fault and Earthquake Research Center, AIST, GSJ), Chair:Bogdan Enescu(筑波大学大学院 生命環境科学研究科 ), Takahiko Uchide(Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology)

3:00 PM - 3:15 PM

[SSS30-17] Resistivity structure and 3He/4He ratios around the focal zone of the 2011 Mw 5.9 earthquake beneath Mt. Fuji, Japan

*Koki AIZAWA1, Hirochika SUMINO2, Makoto UYESHIMA3, Yusuke YAMAYA4, Hideaki HASE5, Masao OHNO1, Masaaki TAKAHASHI4, Kohei KAZAHAYA4, Tawat Rung-Arunwan6, Yasuo OGAWA7 (1.Kyushu University, 2.Geochemical Research Center, Graduate School of Science, University of Tokyo, 3.ERI, University of Tokyo, 4.AIST, 5.GERD, 6.Mahidol University, 7.KSVO, TITECH)

We present the results of a joint 3-D resistivity and isotopic analysis of the groundwater system surrounding Mt. Fuji, Japan, where increased seismicity was observed following the 2011 TohokuOki megathrust earthquake. The electrically conductive zone and high concentrations of magmatic helium correspond to this zone of triggered seismicity. In contrast, 2H (D) and 18O isotope ratios, and Li/Cl ratios do not support the presence of magmatic water. These results suggest that the earthquakes were triggered within a fractured zone where only magmatic gas preferentially travels upward. Although multiple mechanisms may jointly contribute to this remote earthquake generation, we hypothesize that a small fraction of gas bubbles, which are originally secured within the fracture zone by capillary trapping, play a key role for earthquake triggering.