Contemporary Stress Field in the Wadati-Benioff Zone at the Japan-Kurile Arc-arc Junction (North Honshu, the Hokkaido Corner and Hokkaido Island) by Inversion of Earthquake Focal Mechanisms
Contemporary Stress Field in the Wadati-Benioff Zone at the Japan-Kurile Arc-arc Junction (North Honshu, the Hokkaido Corner and Hokkaido Island) by Inversion of Earthquake Focal Mechanisms
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通过地震震源机制反演研究日本-千岛岛弧-弧交界处（本州北部、北海道角和北海道岛）瓦达提-贝尼奥夫带的当代应力场
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发表时间：
2006
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通讯作者：
A. Kato
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作者：
Christova Cenka;N. Hirata;A. Kato
利用Gephart和Forsyth（+32.）的地震震源机制均质资料和反演技术，研究了日本东北部wadti - benio #带和千岛岛最南端的应力场空间分布。使用的数据集包括12/ JMA震源机制解（FMS）和Kosuga et al.（+330）列出的浅层和中深度地震的31个FMS。通过对FMS的P（压缩）轴和T（扩展）轴方向的空间分布进行详细分析，可以勾勒出我们应用应力反演的以下WBZ子体：北本州（NH）和北海道角（HC） WBZ的三个平面结构（平面+，平面，平面-），以及北海道岛（HI） WBZ的上部和下部子体。沿日本东北部和千岛岛弧南部进行了应力场参数评价。平面+应力场以低角度逆冲断层为主，呈现浅倾斜、接近走向正向的最大压缩s+和向下倾斜的最小压缩s-的特征。在NH和HC中，0* 1* km以下的WBZ上表面在平行于s+的板下，沿NH靠近板法线，而在HC中，最小压缩相对于板法线逆时针旋转-*。WBZ的下表面为平面-，其特征为接近板法向s+，接近板平行s-。平面+的应力状态到处都是一般的压缩状态，但在北海道角落下方的HT段则是一般的伸展状态（Guiraud, +323）。平面上的应力状态为一般压缩，平面上的应力状态为纯拉伸。北海道下方的两个WBZ子体的一个特征是，除了岛的南部，上面的子体覆盖着下面的子体。北海道WBZ上亚体的最大和最小压应力方向相对于局部板的几何形状，与NH和HC WBZ的平面+相似，即接近走向法向s+，向下倾斜s-。然而，主应力的倾角在这里是不同的，s+更陡，s更浅。北海道下西北纬z下部亚体应力场特征为走向向北倾斜，方向约为/*，岛南部方向为走向正向，北部方向为板块正向。北海道中部北海道北部北海道北部上分区的P和T向南和向北明显不同于北部上分区的P和T向南和向北，但与北部下分区的P和T向南和向北相似。应力反演结果表明，北海道中部地区WBZ上下亚卷应力场均匀。这里最小压缩的方向（走向对齐，向北）接近于南方* e-mail: cenka@.geophys.bas的方向。bg（保加利亚科学院地球物理研究所，地震学系，Acad. G. Bonchev str. Bl -，保加利亚索非亚+++-）Earthq。东京都大学科学研究所，Vol. 2+,**0 pp. // 1*
This study addresses the space distribution of the stress field in the Wadati-Benio# zone of Northeastern Japan and southernmost Kurile area based on homogeneous data of earthquake focal mechanisms and the inverse technique by Gephart and Forsyth (+32.). The data set used consists of 12/ JMA focal mechanism solutions (FMS) and 31 FMS listed in Kosuga et al. (+330) for shallow and intermediate depth earthquakes. The detailed analysis of the space distribution of orientation of P (compression) and T (extension) axes of FMS allowed the outlining of the following WBZ subvolumes for which we applied the stress inversion : three planar structures in North Honshu (NH) and the Hokkaido corner (HC) WBZ (Plane+, Plane ,, Plane -), and upper and lower subvolumes in the Hokkaido Island (HI) WBZ. The stress field parameters are evaluated along the northeastern Japan and southern Kurile arcs for these WBZ subvolumes. The stress field in Plane +, mainly low-angle thrust faults, is characterized by shallow dipping and close to strike normal maximum compression s+ and down dipping minimum compression s-. Plane ,, the upper surface of the WBZ below 0* 1* km in NH and HC, is under slab parallel s+ and close to slab normal sall along NH, while in HC the minimum compression rotates counterclockwise about -* relative to the slab normal. Plane -, the lower surface of the WBZ, is characterized by close to slab normal s+ and close to slab parallel s-. The stress regime in Plane + is of general compression everywhere but in segment HT, beneath the Hokkaido corner, where it is of general extension (Guiraud, +323). The stress regime in Plane , is of general compression, and in Plane -of pure extension. A characteristic feature of the two WBZ subvolumes outlined beneath Hokkaido is that the upper subvolume overlies the lower one everywhere but in the southern part of the island. The orientations of the maximum and minimum compressive stresses in the upper subvolume of the Hokkaido WBZ, considered relatively to the local slab geometry, are similar to these in Plane + of NH and HC WBZ, i.e. close to strike normal s+ and down dipping s-. However, the dip of the principle stresses is di#erent here s+ is steeper and sis shallower. The stress field in the lower WBZ subvolume beneath Hokkaido is characterized by strike aligned sdipping north at about /* , s+ trends SE being strike normal beneath the southern part of the island and slab normal beneath its northern part. The orientations of P and T in the upper WBZ subvolume in central Hokkaido di#er significantly from these in the upper WBZ volumes to the south and to the north but are similar to those in the lower subvolume here. The stress inversion results indicate homogeneous stress field in the upper and lower WBZ subvolumes beneath central Hokkaido. The orientation of the minimum compression here (strike aligned, trending north) is close to the orientations of sin the southern * e-mail : cenka@.geophys.bas.bg (Geophysical Institute of Bulgarian Academy of Sciences, Dept. of Seismology, Acad. G. Bonchev str. Bl -, Sofia +++-, Bulgaria) Bull. Earthq. Res. Inst. Univ. Tokyo Vol. 2+ ,**0 pp. // 1*