2020 Fiscal Year Research-status Report
Investigation of site amplification at Ocean Bottom stations in the Japan Trench area for earthquake early warning
| Project/Area Number |
20K05055
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| Research Institution | National Research Institute for Earth Science and Disaster Prevention |
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Principal Investigator |
Dhakal Yadab 国立研究開発法人防災科学技術研究所, 地震津波火山ネットワークセンター, 特別研究員 (60708890)
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| Co-Investigator(Kenkyū-buntansha) |
山中 浩明 東京工業大学, 環境・社会理工学院, 教授 (00212291)
若井 淳 国立研究開発法人防災科学技術研究所, マルチハザードリスク評価研究部門, 特別研究員 (20869151)
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| Project Period (FY) |
2020-04-01 – 2023-03-31
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| Keywords | Strong motion prediction / Earthquake early warning / Ocean bottom seismograph / Japan Trench / Site amplification / Damaging earthquakes / S-net / K-NET/KiK-net |
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| Outline of Annual Research Achievements |
We analyzed strong-motion records from selected earthquakes of magnitudes (Mw) 5.3 to 7.0 and described features of strong motions at the S-net ocean-bottom (OB) seismograph sites. We found that the peak accelerations and short-period acceleration response spectra at the OB sites were generally similar to those at the land sites. In contrast, the values for longer periods were larger at the OB sites, on average. The short-period motions at the OB sites were biased to the buried and non-buried stations. We also analyzed moderate magnitude earthquake records at the land sites to compare strong motions from similar earthquakes at the OB sites. We conducted microtremor survey at a reference site on land. We are now deriving site amplifications using the records at the OB sites.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
Our original research plan is slightly behind the schedule mostly due to the COVID19 emergency, which hindered the planned meeting and discussions in the crucial time of beginning the research in 2020. The emergency forced the main investigator to take leaves to take care of the children, and the planned field survey was also delayed as a measure of protection from spreading the COVID 19.
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| Strategy for Future Research Activity |
We have made H/V analysis of earthquake records at all the 150 station of S-net from more than 1000 earthquakes to understand the site characteristics at the S-net sites. We are going to present these results during the September 7-10, 2021 Virtual Annual Meeting of Architectural Institute of Japan, 2021. Journal papers comparing the strong-motion data at the ocean-bottom and land sites are in review. We plan further processing and analyzing the earthquake records at the S-net sites for finding site amplification factors with respect to the reference site on land, and plan the development of ground motion prediction equations by comparing larger data set from the seafloor and land sites.
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| Causes of Carryover |
The virtual conferences due to COVID-19 emergency situation reduced the cost for meeting registrations and travels. The originally planned scale of field survey was also reduced due to COVID-19 emergency situation.
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