中・西部日本の地殻応力

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書誌事項

タイトル別名
  • Crustal Stress in the Central and Western Parts of Honshu, Japan
  • チュウ セイブ ニホン ノ チカク オウリョク

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抄録

We compiled data on the direction of the crustal stress measured in-situ and estimated from shallow (depth≤35km) earthquake focal mechanisms in the central and western parts of Honshu. In the central part of Honshu, the stress data were compiled by Tsukahara and Ikeda in 1991. This report summarizes the stress state in a rather large area: the central and western parts of Honshu. The results are as follows. (1) The stress state estimated from the stress direction and the type of faulting in and around the Izu Peninsula are explained in terms of dynamic interaction between the Philippine Sea (PHS) plate and the Asian (ASA) plate. (2) In the central part of the Kanto plain and the Kanto mountains, the minimum horizontal compressive stress (SHmin) is equal to or smaller than the vertical stress (i. e., tensile stress), and the azimuthal direction is roughly east-west. This stress condition cannot be explained by the westward movement of the Pacific (PAC) plate or the northwestward movement of the PHS plate against the ASA plate. (3) In the areas of the northern part of Kanto, Shin'etsu, Gifu, Hokuriku, and Chugoku, the azimuthal direction of the maximum horizontal compressive stress (SHmax) is west-northwest=east-southeast. Although this direction is approximately the same as that of the movement of the PAC plate, the stress state in these areas is not attributed to the plate movement because (a) some provinces with quite different stress directions lie between the PAC plate and these areas, and (b) SHmin in these areas is tensile stress. It seems that the stress state of this area is dominated by a large scale crustal movement of the Japan Sea or Eastern Asia. (4) In the area of Lake Biwa to Osaka, the stress state is slightly different from that in the areas discussed in (3), i. e., (a) the azimuth of the SHmax direction is approximately east-west, and (b) the type of faulting is different. There are strike-slip and reverse faults as opposed to strike-slip faulting alone for the surrounding area. The reason why this area has its own unique characteristics is not yet understood. (5) In the central Shikoku region, the azimuth of the SHmax direction is approximately east-west and the stress state regime is of the strike-slip faulting type. The east to west SHmax azimuth agrees well with the maximum shortening direction obtained from geodetic surveys in the region during these 100 years, which is attributable to the large crustal deformation at the Nankai Earthquake (1946, M=8.1). In contrast, however, the maximum shortening direction after the earthquake has been north to south. Therefore, the east-west SHmaxazimuth will change to north-south in the future.

収録刊行物

  • 地震　第２輯

    地震　第２輯 44 (3), 221-231, 1991

    公益社団法人 日本地震学会

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