| Project/Area Number |
04452062
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
経済事情及び政策学
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| Research Institution | University of Tokyo |
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Principal Investigator |
OKUBO Shuhei Earthquake Research Institute, University of Tokyo, Associate Professor, 地震研究所, 助教授 (30152078)
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| Co-Investigator(Kenkyū-buntansha) |
MURATA Ichiro Earthquake Research Institute, University of Tokyo, Professor, 地震研究所, 教授 (20012916)
長沢 工 東京大学, 地震研究所, 講師 (40012918)
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| Project Period (FY) |
1992 – 1993
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| Project Status |
Completed (Fiscal Year 1993)
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| Budget Amount *help |
¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1993: ¥500,000 (Direct Cost: ¥500,000)
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| Keywords | Geoid / Plate tectonics / Gravity anomaly / Sea-level |
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| Research Abstract |
1.Theoretical work.
We find an intriguing reciprocity relations between the static deformation excited by a point dislocation in a SNREI earth and those generated by external forces, such as tidal force, surface loading and surface shear forces. the relations enable us to compute the coseismic potential change in a spherically symmetric earth model for the March 28, 1964 Alaska earthquake(mW=9.2). We consider two cases : (1) one is with a barrier where no slip occurs on the fault plane and (2) the other without it. Numerical results clearly indicated that the geoid swells above the subsurface fault while giving a notch over the hidden barrier. Although order of magnitude of these changes are marginal for the present satellite altimetry, there is a good chance of detecting such co-seismic geoid changes if we carefully process satellite altimeter data.
2. Analysis of observational data
We analyzed a gravity anomaly around the North-Izu Fault System (NIFS), Japan Numerical simulation using the theory of coseismic gravity change with geological fault parameters reproduced the local gravity anomaly excellently : positive anomalies over a compressed zone.while negative anomalies over the dilated areas. We conclude the resultant gravity anomaly is the product of repeated coseismic gravity change during a geological timescale because earthquakes will occur on the same fault with the same scheme. However small a coseismic gravity change may be, it is likely to pile up in a systematic way over a long time.
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