Preliminary report of regional resistivity variation inferred from the Network MT investigation in the Shikoku district, southwestern Japan
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- Yamaguchi Satoru
- Department of Earth and Planetary Sciences, Faculty of Science, Kobe University
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- Kobayashi Yoshiaki
- Department of Earth and Planetary Sciences, Faculty of Science, Kobe University
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- Oshiman Naoto
- Disaster Prevention Research Institute, Kyoto University
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- Tanimoto Kengo
- Disaster Prevention Research Institute, Kyoto University
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- Murakami Hideki
- Department of Geology, Faculty of Science, Kochi University
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- Shiozaki Ichiro
- Department of Civil Engineering, Faculty of Engineering, Tottori University
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- Uyeshima Makoto
- Earthquake Research Institute, University of Tokyo
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- Utada Hisashi
- Earthquake Research Institute, University of Tokyo
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- Sumitomo Norihiko
- Disaster Prevention Research Institute, Kyoto University
書誌事項
- タイトル別名
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- Preliminary report on regional resistivity variation inferred from the Network MT investigation in the Shikoku district, southwestern Japan
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The Network MT method was used in the eastern part of the Shikoku district, southwestern Japan, and a total of thirty-nine MT impedances (64 to 2560 sec) were obtained. These MT impedances had their values averaged over a triangular element, whose sides were a few kilometers long with geomagnetic observatory data from the Kakioka Geomagnetic Observatory. Well-determinedMTimpedances varied from north to south with the greatest differences being at the Median Tectonic Line, which is consistent with the surface geology in the area. In addition, very large or very small values of apparent resistivity were obtained in some triangular elements. These triangles were located on a cape or near an estuary, with effects of three-dimensionality clearly apparent. Stable MT impedances were not obtained for three groups of triangular elements: (1) those where one or two sides of the triangular element cross the coast; (2) those where the electric field was contaminated by severe artificial noise, these were mainly in the northwestern part of the survey area; (3) those where the triangles had an extremely acute- or obtuse-angle. A resistivity cross section was derived from the TM-mode data for a profile crossing the eastern part of the area. The shallower layer, which approximately corresponds to the crust, was divided into three blocks. Two resistive boundaries coincide with the geological tectonic lines and the strong horizontal contrast found at the Median Tectonic Line. The northernmost block is the most resistive, and the block to the south is the most conductive. Beneath these blocks, the subducting Philippine Sea plate was represented by a thick and highly resistive north-dipping layer. A highly conductive thin layer was found above the resistive layer on the southern side of the Median Tectonic Line. This layer is only found beneath the southern side of the Median Tectonic Line and is probably caused by pore water and/or sediment at the upper plane of the subducting Philippine Sea plate. Another conductive layer was found under the highly resistive north-dipping layer. The resistivity structure from the lower crust to the upper mantle is firstly obtained using the Network-MT method. However, further developments are needed in methods of data analysis, which are robust to artificial electric noise, in order to clarify the spatial distribution of MT impedances in the complete study area.
収録刊行物
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- Earth, Planets and Space
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Earth, Planets and Space 51 (3), 193-203, 1999
地球電磁気・地球惑星圏学会 、公益社団法人 日本地震学会、特定非営利活動法人 日本火山学会、日本測地学会、日本惑星科学会
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詳細情報 詳細情報について
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- CRID
- 1390282681485529600
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- NII論文ID
- 10003737535
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- NII書誌ID
- AA11211921
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- ISSN
- 18805981
- 13438832
- http://id.crossref.org/issn/13438832
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- NDL書誌ID
- 4717079
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- 本文言語コード
- en
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- データソース種別
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- JaLC
- NDL
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