Japan Geoscience Union Meeting 2016

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Poster

Symbol S (Solid Earth Sciences) » S-CG Complex & General

[S-CG57] Geofluids and dynamics in subduction zones

Tue. May 24, 2016 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall HALL6)

Convener:*Ikuo Katayama(Department of Earth and Planetary Systems Science, Hiroshima University), Atsushi Okamoto(Graduate School of Environmental Studies), Tatsuhiko Kawamoto(Institute for Geothermal Sciences, Graduate School of Science, Kyoto University), Junichi Nakajima(Department of Earth and Planetary Sciences, Tokyo Institute of Technology)

5:15 PM - 6:30 PM

[SCG57-P07] Effect of pore fluid on seismic velocity of serpentinite and the origin of high Vp/Vs in mantle wedge

*Ikuo Katayama1, Yunxi Liu1, Kanta Zaima1 (1.Department of Earth and Planetary Systems Science, Hiroshima University)

Keywords:serpentinite, seismic velocity, pore fluid

Serpentine is one of the candidates to explain low-velocity anomaly and high Vp/Vs in mantle wedge. However, extremely high Vp/Vs found beneath Kanto and southwest Japan requires the presence of aqueous fluid in addition to the serpentinites. In this study, we investigated the effect of pore fluid on elastic-wave velocity of antigorite during triaxial deformation using intra-vessel apparatus at Pc = 10-20 MPa, Pp = 5-10 MPa and room temperature. Compressional and shear-wave velocities decrease during deformation, possibly due to the formation of micro-cracks in the specimen. Since shea-wave velocity changes more drastically than compressional-wave velocity, Vp/Vs increases during deformation, which is consistent with the crack model by O’Connel and Budiansky (1974). In future, we are going to monitor volume change of pore fluid during deformation, and discuss the amounts of pore fluid to explain the observation of high Vp/Vs in mantle wedge.