1995 Fiscal Year Final Research Report Summary
Analysis of dynamic behavior of interactive fault system and estimate of high frequency strong motion
| Project/Area Number |
06680423
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Natural disaster science
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| Research Institution | University of Tokyo |
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Principal Investigator |
YAMASHITA Teruo Earthquake Research Institute, University of Tokyo, Professor, 地震研究所, 教授 (10114696)
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| Co-Investigator(Kenkyū-buntansha) |
UMEDA Yasuhiro Disaster Prevention Research Institute, Kyoto University, Associate Professor, 防災研究所, 助教授 (10025421)
MIYATAKE Takashi Earthquake Research Institute, University of Tokyo, Associate Professor, 地震研究所, 助教授 (60126183)
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| Project Period (FY) |
1994 – 1995
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| Keywords | fault / crack / strong motion / interactions / rupture |
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| Research Abstract |
The critical slip displacement D_c is defined as the amount of relative slip required for the shear stress to decrease to the residual stress level. It is indicated that there is a discrepancy between laboratory measurements of D_c and values obtained from modeling earthquakes. Our theoretical analysis has shown that the existence of a thick fault zone for natural earthquake is likely to contribute this discrepancy.
We also theoretically studied the dynamic nucleation of an earthquake in a fault zone in which small preexisting cracks are densely distributed. Dynamic rupture nucleated in such a zone is significantly influenced by the crack interactions. In general, crack interactions cause two conflicting effects : One is to promote crack growth, and the other to decelerate it. These two are due to coplanar and non-coplanar crack interactions, respectively. Hence if non-coplanar interactions are predominant at the initial state, the crack growth rate is very slow at its onset as shown in our simulations. Observation of seismic quiescence before a large earthquake implies that the assumption that non-coplanar crack interactions prevail at initial state will be reasonable.
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