1999 Fiscal Year Final Research Report Summary
Study on the thermal anomaly due to active faulting
| Project/Area Number |
09640507
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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 |
固体地球物理学
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
TAGAMI Takahiro Graduate School of Science, KYOTO UNIVERSITY Associate Prof., 大学院・理学研究科, 助教授 (80202159)
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| Co-Investigator(Kenkyū-buntansha) |
HASEBE Noriko Kanazawa Univ., Department of Geology, Assistant Prof., 理学部, 助手 (60272944)
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| Project Period (FY) |
1997 – 1999
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| Keywords | Earthguake / Nojima Fault / Thermal anomaly / Thermochronology / Fission track / Zircon |
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| Research Abstract |
To better understand the heat generation and transfer along earthquake fault, we measured zircon fission-track (FT) length data from Nojima fault, Awaji-shima Island, Japan, which was activated during the 1995 Kobe earthquake (Hyogo-ken Nanbu earthquake). Samples were collected from Cretaceous granitic rocks at depths using the Ogura 500 m borehole and Geological Survey of Japan (GSJ) borehole, as well as at outcrops nearby the boring sites. The Nojima fault plane was drilled at 389.4 m depth (along-core apparent depth) for Ogura and at about 625 m for GSJ. For Ogura samples, FT lengths in zircons from localities>60 m away from the fault plane as well as those from outcrops are characterized by the mean values of 〜10-11 μm and unimodal distributions with positive skewness, showing no signs of appreciable reduction of FT length. In contrast, those from nearby the fault at depths show significantly reduced mean of 〜7-8 μm and distributions having a peak around 6-7 μm with rather negative skewness. A similar trend was observed for GSJ samples, in which the peak around 6-7 μm is less dominant however. In conjunction with other geological constraints, these results are best interpreted by the recent thermal anomaly around the fault, which is attributable to the frictional heating of fault motion and/or heat transfer via fluids from the deep interior of the crust.
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[Publications] Sudo, M., Listanco, L. L., Ishikawa, N., Tagami, T., Kamata, H. and Tatsumi,Y: "K-Ar dating of the volcanic rocks from Macolod Corridor in southwestern Luzon, Philippines : toward understanding of the Quaternary volcanism and tectonics."Philippine J. Earth Sci. (in press). (2000)
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