Frictional property of plate interface east off NE Japan inferred from spatial variation in b-value

概要

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Simultaneous evolutions of AE activityon a pre-cut fault and frictional properties of the fault with sliding were observed in a laboratory. The evolutions are probably due to brittle evolution of fault surfaces. It is reported in literature that the b-value of shallow earthquakes east off NE Japan varies with distance from the trench-axis. Because the distance from the trench-axis is regarded as a displacement of the subducting slab, the b-value variation is considered to be a similar phenomenon to the evolution of AE activityin the laboratory. The spatial variation of the b-value is examined to estimate the upper limits of the unstable region on the plate interface. The depths of estimated upper limits are 20km on average, and varylaterallyto depict unstable regions estimated from other seismological and geodetic evidence. The present studysuggests that detailed analyses of high-qualityseismic data provide useful information about the mechanical properties of the plate interface.