| Project/Area Number |
02302025
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| Research Category |
Grant-in-Aid for Co-operative Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体地球物理学
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| Research Institution | Tokai University |
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Principal Investigator |
UYEDA Seiya Tokai Univ., Sch. Mar. Sci. Tech., Professor, 海洋学部, 教授 (60011459)
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| Co-Investigator(Kenkyū-buntansha) |
KINOSHITA Masataka Tokai Univ., Sch. Mar. Sci. Tech., Research Associate, 海洋学部, 助手 (50225009)
UYESHIMA Makoto 防災科学技術研究所, 特別研究員
UTADA Hisashi Univ. Tokyo, Earthq. Res. Inst., Associate Professor, 地震研究所, 助教授 (70134632)
NAGAO Toshiyasu Kanazawa Univ., Faculty of Sci., Research Associate, 理学部, 助手 (20183890)
KONO Yoshiteru Kanazawa Univ., Faculty of Sci., Associate Professor, 理学部, 助教授 (80019489)
宮腰 潤一郎 鳥取大学, 教養部, 教授 (60032116)
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| Project Period (FY) |
1990 – 1991
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| Project Status |
Completed (Fiscal Year 1991)
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| Budget Amount *help |
¥9,700,000 (Direct Cost: ¥9,700,000)
Fiscal Year 1991: ¥4,300,000 (Direct Cost: ¥4,300,000)
Fiscal Year 1990: ¥5,400,000 (Direct Cost: ¥5,400,000)
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| Keywords | VAN-method / Earthquake prediction / Earth current / NTT / Swarm earthquakes off Izu Peninsula / Electrical conductivity / Izu Oshima / MT-method / 自然電位 / 地震 / 確率差分方程式 |
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| Research Abstract |
Recognizing that short-span dipole observations with different dipole length, which is absolutely necessary for the VAN-method, we put major effort in the present research program to the following two areas ; i. e. Hokuriku region, which is conveniently located for some researchers, and Izu Oshima Island, where some interesting results were obtained earlier. In the former area, 14 stations are now in operation. Noisewise these stations are as quiet as VAN stations in Greece. So far, no firm results have been obtained on SES, mainly because there have been no sizable (M>5) event in the region. In the latter, many local short and long-span dipoles have been installed on the Island. Some anomalous changes similar in character as those, which showed an increased occurrence before the Off East Izu seismic swarms in the past, were shown to be localized changes near Okata NTT dipole. But these changes were not correlated with earthquakes either. The nature of the changes in question will not be known until th next swarm comes.
In the present research, a NETWORK MT method has been developed through an extensive use of NTT electrodes. The method has clarified th subterranean electrical conductivity structure under Hokkaido with unprecedented scale and reliability. Not only to th VAN research, this was a great contribution to th solid earth geoscience in general. In the future, to know th sensitivity of a station beforehand, we want to make, in cooperation with th VAN scientists, thorough comparative geophysical and geological surveys in both sensitive and insensitive areas in Greece to see if there is any systematic difference between them.
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