[SSS10-P11] Linear distribution of the intraslab earthquakes in Tokai
Keywords:intraslab earthquakes , linear distribution of earthquakes , oceanic mantle
Figure 2 is a seismological cross section that crosses the Tokai area from NNW to SSE referred from Suzuki et al., 2018. Schematic interpretation of seismic structures including S wave tomography (Nakajima and Hasegawa, 2016) and two earthquake groups consisiting of LFEs and intraslab earthquakes are represented. The most of intraslab earthquakes distributes in the low velocity area of S wave in the uppermost oceanic mantle. The relatively low velocities of S wave in the subducting oceanic crust and its surrounding areas are interpreted as being indicative of fluids released by progressive metamorphic dehydration reactions in the oceanic crust (e.g., Abers et al., 2013) under increasing temperature and pressure conditions. We suppose that the intraslab earthquakes occur because these fluids penetrate into the uppermost oceanic mantle. Therefore the pore fluids may penetrate from the oceanic crust into not homogeneously but linearly in plane. It is presumed that old fracture zones that had been formed before the Philippine Sea plate subducted below the Tokai area existed at the uppermost oceanic mantle.
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