Japan Geoscience Union Meeting 2015

Presentation information


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

[S-CG62] Slow earthquakes

Wed. May 27, 2015 4:15 PM - 6:00 PM 303 (3F)

Convener:*Hitoshi Hirose(Research Center for Urban Safety and Security, Kobe University), Kazushige Obara(Earthquake Research Institute, The University of Tokyo), Ryoko Nakata(Japan Agency for Marine-Earth Science and Technology), Chair:Tetsuya Takeda(National Research Institute for Earth Science and Disaster Prevention), Hitoshi Hirose(Research Center for Urban Safety and Security, Kobe University)

5:00 PM - 5:15 PM

[SCG62-11] Tremor activity and slip modes controlled by the permeability of the megathrust boundary

*Junichi NAKAJIMA1, Akira HASEGAWA1 (1.Graduate School of Sci. Tohoku Univ.)

Keywords:permeability, Philippine Sea plate

Tremor activity in southwest Japan shows a sharp variation along the strike, but factors controlling such variation remain largely unknown. We carry out seismic tomography using a large number of arrival time data to characterize seismic properties around tremor activity, and find a close link between tremor activity and seismic properties above the plate interface. Tremor is active underneath the moderate- to high-velocity overlying plate, while it is absent in areas overlain by distinct low-velocity materials. High permeability along the plate interface enhances metamorphism of the overlying plate and prevents pore-fluid pressures from reaching near-lithostatic values. As a result, the plate interface is somewhat strengthened and slow slip no longer occurs at short intervals. Our hypothesis explains the occurrence of long-term slow slip, instead of short-term slow slip, along the inferred high-permeable plate interface in the Kii channel and eastern Kyushu.