Study of thermal processes of seismogenic regions in the subduction zone by thermochronology and calcite-vein analysis

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In order to assess quantitatively the heat generation and transfer associated with fault motions, thermochronologic analysis was conducted on the ancient seismogenic-zone fault which juxtaposes the underlying Okitsu melange unit and overlying coherent Nonokawa unit. The length and age analyses of zircon fission tracks unraveled that a zone of shortened tracks and younger ages due to secondary heating was widely distributed within about 20m away from the fault plane. Thermal history inversion and other analyses suggest that the secondary heating event was resulted from the hot fluid migration from deep crustal interiors, which is likely associated with fault motions of the out-of sequence thrust.