| Project/Area Number |
17540401
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Solid earth and planetary physics
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| Research Institution | Building Research Institute |
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Principal Investigator |
BUNICHIRO Shibazaki Building Research Institute, INTERNATIONAL INSTITUTE OF SEISMOLOGY AND EARTHQUAKE ENGINEERING, CHIEF SIESMOLOGIST (20344012)
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| Project Period (FY) |
2005 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥2,680,000 (Direct Cost: ¥2,500,000、Indirect Cost: ¥180,000)
Fiscal Year 2007: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000)
Fiscal Year 2006: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2005: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Keywords | SHORT-TERM SLOW SLIP EVENT / MODELLING / RATE AND STATE-DEPENDENT FRICTION LAW / UNSTABLE-STABLE TRANSITION / HIGH PORE-FLUID PRESSURE / NANKAI SUBDUCTION ZONE / CASCADIA SUBDUCTION ZONE / VERY-LOW-FREQUENCY EARTHOUKES / ゆっくりすべり / 沈み込みプレート境界 / 摩擦構成則 / カスケード / 南海トラフ |
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| Research Abstract |
Recent high-resolution observations of crustal movements have revealed short-term slow slip events (SSEs) with intervals of 3-14 months along the deeper parts of the Cascadia and Nankai subduction zones. This study develops models of these short-interval SSEs considering the frictional behaviour that was confirmed experimentally for the unstable-stable transition regime. lb represent the frictional behaviour, a small cut-off velocity to an evolution effect is introduced in a rate and state-dependent friction law. When the cut-off velocity to the evolution effect is significantly smaller than that to a direct effect, steady-state friction exhibits velocity weakening at low slip velocities and velocity strengthening at high slip velocities. In conditions where the pore-fluid pressure is nearly equal to the lithostatic pressure and the critical weakening displacement is very small, short-interval silent slip events with propagation velocity of 10km/day can be reproduced. We have also developed a model of short-term SSEs on the 3D subduction interface beneath Shikoku, western Japan. From the epicentral distribution of deep, low-frequency tremors, we set the width of the generation zone of SSEs such that it is wider beneath the western part of Shikoku than the eastern part of Shikoku. We can reproduce events with longer lengths in the horizontal direction beneath the western part of Shikoku with longer recurrence times. The numerical results are consistent with the observations in that the events at longer segments have longer recurrence intervals. We have also attempted to model the very-low-frequency earthquakes that are accompanied by short-interval SSEs. In order to model such earthquakes, we consider a local patch where the critical displacement is very small. We confirm that high-speed multiple slips occur in the local patch with a small critical displacement with the occurrence of short-interval SSEs.
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