| Project/Area Number |
14380032
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
自然地理学
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| Research Institution | HIROSHIMA UNIVERSITY |
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Principal Investigator |
NAKATA Takashi Hiroshima University, Graduate School of Letters, Professor, 大学院・文学研究科, 教授 (60089779)
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| Co-Investigator(Kenkyū-buntansha) |
KUMAMOTO Takashi Okayama University, Faculty of Science, Associate Professor, 理学部, 助教授 (60285096)
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| Project Period (FY) |
2002 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥6,000,000 (Direct Cost: ¥6,000,000)
Fiscal Year 2004: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2003: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 2002: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Keywords | active fault / directivity effect / segmentation / fault branching / fault rupture process / strong motion simulation |
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| Research Abstract |
Defining fault-zone segments and evaluating the reliability of individual segment boundaries to stop propagating ruptures are essential for accurate size estimation of future earthquakes generated from active faults. Direction of rupture propagation is closely related to strong ground motions and resulting earthquake damage. Therefore, predicting earthquake rupture length and directivity are crucial in mitigating earthquake damage. However, they were mostly ascertained only after earthquakes from the observed seismological records and not before the earthquakes.
The purpose of this study is to propose a behavioral model of active faults from their geometric pattern for simulating earthquakes associated with surface ruptures. Nakata and Goto (1998) proposed the geometric criteria such as (1)branching features of active fault traces and (2)characteristic pattern of vertical-slip distribution along the fault traces as tools to predict rupture length of future earthquakes. The branching dur
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ing the fault rupture propagation is regarded as an effective energy dissipation process and could result in final rupture termination.
We name this conceptual model as "Morphometric Unit Model" and call active faults grouped by the model as "Packaged Faults" for individual seismogenic faults. By applying these new geometric criteria to the high-resolution active fault distribution maps, the fault grouping/segmentation could be more practically conducted. Kashima fault in Shimane Peninsula, SW Japan is revealed as one of the most typical examples for this model. We also tested this model successfully on the seismogenic fault that generated the 1943 Tottori earthquake, the Chojagahara-Yoshii fault zone in Chugoku district in Japan, as well as the active fault system in northern Luzon, the Philippines.
With this model in mind, we conducted detailed mapping of active faults in Japan as potential seimogenic faults. The active faults mapped were digitized, and used for seismic risk assessment for public buildings and national treasures.
Magnitude-frequency distribution generated from the active faults was estimated based on the digitized active faults data. Strong ground motion was also simulated from the parameter of the earthquakes from the active fault system of the Median Tectonic Line in Shikoku segmented following the result of this study. Less
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