2007 Fiscal Year Final Research Report Summary
Ground Structure and Strong Motions in the Grenoble Basin
| Project/Area Number |
18404006
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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 | 海外学術 |
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| Research Field |
Natural disaster science
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| Research Institution | KYUSHU UNIVERCITY |
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Principal Investigator |
KAWASE Hiroshi KYUSHU UNIVERCITY, Faculty of Human-Environment Studies, Professor (30311856)
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| Co-Investigator(Kenkyū-buntansha) |
IWATA Tomotaka Kyoto University, Disaster Prevention Research Institute, Professor (80211762)
IRIKURA Kojiro Kyoto University, Professor Emeritus (10027253)
SATO Toshiaki Shimizu Corporation, Institute of Technology, Senior Researcher (80393560)
SATOH Toshimi Shimizu Corporation, Institute of Technology, Chief Researcher (00393562)
SASATANI Tsutomu Hokkaido University, faculty of Engineering, 教授 (10002148)
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| Project Period (FY) |
2006 – 2007
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| Keywords | Array Microtremors / Strong Motions / Sedimentary Basin / Grenoble / Underground Structure |
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| Research Abstract |
What we would like to clarify in the present study is whether the estimation of strong ground motion and the estimation of damage scheme that Japan has developed aggressively in these years are similarly effective in Europe where the geological environment is different very much from Japan. To this end we investigated the underground structure of the Grenoble basin by using microtremor measurement in cooperation with the Grenoble University in France who offered us a joint research for the purpose. We then perform ground motion prediction study for the Grenoble city. It is expected to show that the strong ground motion prediction technology that has been developed as a Japanese original technology has the generality that can be applied to the region where the geological environment is quite different.
The extremely long duration of the seismic ground motion were observed in the Laffrey 2005 event that had been occurred in the south of the Grenoble basin in 2005. We first extract information of duration and wave energy in comparison to the other events. We also use simulation results of the three-dimensional finite difference methods for the Grenoble basin. It was able to be pointed out that a long duration can be introduced if we assume considerably weak surface layers on top of the surrounding rock formations. As is quite natural an introduction of soft layers on top of sediments makes duration even longer and successfully reproduces durations at most of the site within the basin. However, very long duration in the northeastern part of the basin can only be explained by considering the very soft, weathered layer.
On the other hand, it has been understood that the analysis of the ground survey in the region is advanced, and a weak surface of the layer thickness of about 25m exists in the surface in boring and the array measurement of microtremors. Therefore, the possibility of the soft surface sediments is high that create very long duration in the observed waveforms.
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