| Project/Area Number |
08640529
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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 | Toyama University |
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Principal Investigator |
KAWASAKI Ichiro Toyama University, department of Earth Sciences, Professor, 理学部, 教授 (60115136)
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| Co-Investigator(Kenkyū-buntansha) |
OKADA Yoshimitsu Earthquake Rexearch center, National Institute of Disaster Prevention Research,, 地震調査研究センター, センター長
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| Project Period (FY) |
1996 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1997: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1996: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Keywords | slow earthquake / crustal movement / strain step / seismic coupling / seismo-geodetic coupling / Sanriku-Oki earthquake / gap of moment release / mid-term / long-term prediction / プレート間モーメント / サイスミックカップリング |
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| Research Abstract |
We had the 1989,1992 and 1994 Sanriku-Oki earthquakes in the region form 39.0ﾟN to 40.6ﾟ N along the Japan trench. Summarizing the aseismic nature of the earthquakes, we propose two new concepts "seismo-geodetic coupling" and "a gap of the moment release". The sum of their seismic moments is (4.8-6.6) *10^<20>Nm.
These events were associated with aseismic ultra-slow faulting of source times of a day to a year following the respective main seismic shocks. The ultra-slow faultings respectively released interplate moments, 1.4, (1-4), 4.2*10^<20>Nm, equivalent to those of Mw7.3 to 7.7 seismic events. The sum of the moments released by both seismic and aseismic faultings amounts to (11-16) *10^<20>Nm.
The interplate moment is accumulated as (19-23) *10^<20>Nm for the area of 180km (39.0ﾟ N to 40.6ﾟN) *150km (width of high seismicity region between the Sanriku coast and the Japan trench), with the relative plate motion of 8 cm/yr and the interval of 21-27 years from the 1968 Tokachi-Oki earthquake of Mw8.2 to the 1989-1994 ultra-slow earthquakes.
The ratio of (11-16) *10^<20>Nm to (19-23) *10^<20> Nm leads to the rough estimate of "seismo-geodetic coupling coefficient" of 50-85%, where the ordinary seismic coupling coefficient has been estimated to be 20-30% between the Okhotsk and subducting Pacific plates.
Based on the spatiotemporal distribution of the interplate moments including the ultra-slow earthquakes, three gaps of the moment release are suggested for the Sanriku-Oki region. This would serve as a basis for the mid-term/long-term prediction of future interplate earthquakes in the Sanriku-Oki region.
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