【摘要】 基于粘弹性平面应变有限元数值模拟方法 ,研究了俯冲带深部的应力场特征 .当根据Karato等的研究结果给出俯冲板块的粘度结构时 ,橄榄石—尖晶石相变界面以下中心低粘区两侧出现应力集中区 ,而且其主压应力方向沿俯冲方向走向 .其特征与已有的深源地震主压应力方向沿俯冲方向及深源地震有两个条带的地震观测结果相吻合 .相变过渡区因矿物更小的颗粒粒度而导致的更小的等效粘度对俯冲带深部应力场的影响不大 ;存在和不存在亚稳态橄榄石楔的情况下 ,橄榄石—尖晶石相变过渡区附近都有最大剪应力的最大值出现 ,而其主压应力方向有垂直于橄榄石—尖晶石相变过渡区走向的趋势 ,尚与地震观测资料不符更多还原

【Abstract】 Using a 2-D plain strain viscoelastic FEM code, we study the characteristics of the stress fields in deep subducting slabs. There are maxima of shear stress at the transition region from olivine to spinel, the direction of the maximum compressional stress of which is roughly along the trend of the phase boundary. When we introduce the new rheology structure given by Karato et al into our computation, two new maxima of shear stress appear just below the olivine-spinel transition zone, which encompass the low viscosity zone below the tip of metastable wedge. It is needed to mention that the directions of the maximum compressional stress of these two regions are all along the dip direction of the subducting slab. This new feature of stress state in the subducting slab reveals a new way to explain the deep seismicity.更多还原