Dissecting large earthquakes in Japan: Role of arc magma and fluids |
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| Authors: | Dapeng Zhao M Santosh and Akira Yamada |
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| Institution: | Department of Geophysics, Tohoku University, Sendai 980-8578, Japan,;Department of Natural Environmental Science, Kochi University, Kochi 780-8520, Japan, and;Geodynamics Research Center, Ehime University, Matsuyama 790-8577, Japan |
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| Abstract: | We synthesized information from recent high-resolution tomographic studies of large crustal earthquakes which occurred in the Japanese Islands during 1995–2008. Prominent anomalies of low-velocity and high Poisson's ratio are revealed in the crust and uppermost mantle beneath the mainshock hypocenters, which may reflect arc magma and fluids that are produced by a combination of subducting slab dehydration and corner flow in the mantle wedge. Distribution of 164 crustal earthquakes ( M 5.7–8.0) that occurred in Japan during 1885–2008 also shows a correlation with the distribution of low-velocity zones in the crust and uppermost mantle. A qualitative model is proposed to explain the geophysical observations recorded so far in Japan. We consider that the nucleation of a large earthquake is not entirely a mechanical process, but is closely related to the subduction dynamics and physical and chemical properties of materials in the crust and upper mantle; in particular, the arc magma and fluids. |
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| Keywords: | arc magma fluids large earthquakes mantle wedge seismic tomography slab dehydration |
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