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在日本西南的板内地区发现了最大主应力轴(σ1)方位角的空间变化。根据大量精确震源机制进行应力反演推测,沿日本海岸地震带的σ1轴方位角取向为N110°E～N130°E,而在周边地区几乎为东西方向,即N90°E～N100°E。沿南海海沟内陆板块的地壳浅部广泛观测到东西方向的最大水平压应力。然而,在该地震带上仅观测到WNW—ESE方向的最大水平应力。用该地震带之下下地壳中的无震断层或延性断层带的形变解释了该地震带内及其周围应力场的这种空间变化。
The spatial variation of the azimuth of the axis of maximum principal stress (σ1) was found in the intraplate region of southwestern Japan. According to the stress inversion of a large number of accurate focal mechanisms, it is inferred that the azimuthal orientation of the sigmoidal axis along the Japan Seismic Seismic Belt is N110 ° E ~ N130 ° E, whereas it is almost east-west in the surrounding area, that is, N90 ° E ~ N100 ° E. The maximum horizontal compressive stress in the east-west direction was widely observed along the shallow crust of the South China Sea trench inland plate. However, only the maximum horizontal stress in the WNW-ESE direction was observed on the seismic belt. The spatial variation of the stress field in and around the seismic zone is explained by the deformation of the seismic-free fault or ductile fault zone in the lower crust beneath the seismic zone.