第121回ジオダイナミクスセミナー
　　　Geodynamics　Seminar

　 　　　　"Stress regime and anisotropy in deep slabs"

　　　 　 講師：Sihua Zheng(GRC外国人研究員(客員))

　　　　　　　　　　　　 　　　　　 　　　　　
　　　　　主催　：　愛媛大学地球深部ダイナミクス研究センター
　　　　　日時　：　２００５年３月１１日（金）17：00〜
　　　　　場所　：　愛媛大学総合研究棟1Ｆ　情報処理室

要　旨
　We investigated the stress regime and anisotropy in deep slabs of the main subduction zones in the world, utilizing the Harvard CMT (Centroid Moment Tensor) solutions from 1976 to 2004. In stress inversion the FMSI (Focal Mechanism Stress Inversion) technique (Gephart, 1990) is used to retrieve the stress tensor orientation from the double-couple components of CMT solutions. In anisotropy inversion the method proposed by Vavrycuk (2004) is used for retrieving the anisotropic elastic parameters in the source region and orientations of anisotropic symmetry axes from the non-double-couple components of CMT solutions. The result shows that (1) generally, within deep slabs the maximum stress is oriented along the direction of subducting of slab; the minimum stress is perpendicular to the plane of the slab; and the intermediate stress is oriented along the strike direction of slabs; (2) the slab above seismic gap near 410 km discontinuity in some slabs, has a different stress regime from the deep slab; (3) the directions of anisotropic symmetry axes generally coincide with or close to the principal stress directions; (4) the values of anisotropy strength in deep slabs are higher than those in the surrounding mantle by S wave splitting analysis. These results may enable us to better understand the dynamic characteristics of subducting slabs in deep.





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