2005 Fiscal Year Final Research Report Summary
Study on mechanism of tsunami earthquakes by using ocean-bottom seismometers and pressure gauges
| Project/Area Number |
15540414
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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 |
Solid earth and planetary physics
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| Research Institution | Independent Administrative Institution, Japan Agency for Marine-Earth Science and Technology |
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Principal Investigator |
HIRATA Kenji IFREE/JAMSTEC, Researcher, 地球内部変動研究センター, サブリーダー (20359128)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUMOTO Hiroyuki IFREE/JAMSTEC, Researcher, 地球内部変動研究センター, 研究員 (80360759)
BABA Toshitaka IFREE/JAMSTEC, Researcher, 地球内部変動研究センター, 研究員 (90359191)
TANIOKA Yuichiro Hokkaido Univ., Assistant Professor, 地震火山観測研究センター, 助教授 (40354526)
SATAKE Kenji AFRC/AIST, Sub Leader, 活断層研究センター, 副センター長 (20178685)
TAKAHASHI Hiroyuki Hokkaido Univ., Assistant, 地震火山観測研究センター, 助手 (30301930)
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| Project Period (FY) |
2003 – 2005
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| Keywords | pressure gauge / tsunami / micro-tsunami / thermal response / temperature correction |
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| Research Abstract |
The purpose of this study was to detect micro-tsunamis on the basis of analyses of ocean-bottom pressure gauge data, and then to examine the mechanism of tsunami earthquakes. However, we encountered a problem that was not known before so that we could not touch the second purpose but complete the first purpose. The problem is that pressure gauges have inherent transient thermal responses affecting pressure measurements. Inherent thermal response yields a large pseudo-pressure signal, with periods overlapping to major periods of tsunami, when temperature suddenly changes. Therefore, evaluation and correction of the transient thermal response is inevitable for ocean-bottom pressure measurements, in particular for real-time offshore tsunami monitoring. To overcome this, we devised a new empirical method to estimate transient thermal responses, and then checked its validity by using observed ocean-bottom pressure and temperature. An article showing the method result was accepted by Geophys
… More
ical Research Letter and now in press.
Next, we investigated maximum amplitudes of observed micro-tsunamis, and compared those with maximum amplitudes of coastal tide gauge records in Japan. Because tsunami magnitudes (Mt) applicable to offshore tsunamis was not defined yet, we extended definitions of tsunami magnitudes by Abe(1979,1981) to get new definitions appropriate for offshore tsunamis on the basis of theoretical considerations. The new definitions were evaluated by comparing the new Mt scale with original Mt scale. The article regarding to the new Mt definition was published in 2003.
Finally, we tried to detect and identify micro-tsunamis from continuous records of ocean-bottom pressure gauges off Tokachi, Japan. Because of limitation of computing resources, we examined 2-year-long pressure data with a 1-minutes-sampling rate. We identified total of 14 possible micro-tsunam is, all of which occurred landward of 3000 m iso-bathymetry line. None of them occurred in accretion prism near the trench. Because tsunami earthquakes are widely believed to occur in accretion prism or the plate interface below the prism, all of 14 micro-tsunamis are seemed not to be tsunami earthquakes. A future examination if these micro-tsunamis are tsunami earthquakes or not will be needed. Less
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[Journal Article] Tsunami source of the 2004 off the Kii Peninsula earthquakes inferred from offshore tsunami and coastal tide gauges2005
Author(s)
Satake, K., T.Baba, K.Hirata, S.Iwasaki, T.Kato, S.Kosimura, J.Takenaka, Y.Terada
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Journal Title
Earth, Planets, Space 57
Pages: 178-183
Description
「研究成果報告書概要(和文)」より
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[Journal Article] Tsunami source of the 2004 off the Kii Peninsula earthquakes inferred from offshore tsunami and oastal tide gauges2005
Author(s)
Satake, K., T.Baba, K.Hirata, S.Iwasaki, T.Kato, S.Kosimura, J.Takenaka, T.Terada
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Journal Title
Earth, Planets, Space 57
Pages: 183-178
Description
「研究成果報告書概要(欧文)」より
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