3-D Simulation of Tectonic Loading at Convergent Plate Boundary Zones: Internal Stress Fields in Northeast Japan |
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| Authors: | Chihiro Hashimoto Mitsuhiro Matsu'ura |
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| Institution: | (1) Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan |
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| Abstract: | The evidence of east-west compression in northeast Japan has been reported by many investigators on the basis of geodetic,
geologic and geomorphic data, but its origin still remains far from understood. In the present study we have proposed a mechanical
model of tectonic loading at convergent plate boundary zones, and demonstrated its validity through the numerical simulation
of internal stress fields in northeast Japan with realistic 3-D geometry of plate interfaces. At convergent plate boundary
zones, in general, a part of plate convergence is consumed by steady slip along plate interfaces, and the remaining part by
inelastic deformation (seismic faulting, aseismic faulting, and active folding) of overriding plates. Such a plate boundary
process to be called ``partial collision' can be quantitatively described by introducing a collision rate defined as c = 1 − steady slip rate at plate interfaces/plate convergence rate. By this definition, we can simply represent the mechanical process of partial collision, which includes total subduction
(c = 0) and total collision (c = 1) as two extreme cases, in terms of steady slip rates at plate interfaces. On the basis of elastic dislocation theory,
first, we numerically computed the internal stress fields in northeast Japan produced by the total subduction of the Pacific
plate beneath the North American plate, however the computed stress pattern was opposite in sense to observations. Then, we
computed the internal stress fields by taking c = 0.1 on average, and succeeded in reproducing the observed east-west compression in northeast Japan. This indicates that
the concept of partial collision is essential to understand the mechanism of intraplate tectonic loading. |
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| Keywords: | Plate convergence partial collision collision rate tectonic loading elastic dislocation theory |
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