地幔物质上涌引起断层强度的变化和分布

本文根据多孔介质弹性变形与流体扩散在力学上的相互作用,选取了耦合本构关系式作为数学模型并对其求解,研究了地壳中三种类型断层在地幔物质上涌作用下,所产生的附加断层强度的变化和分布。主要结果是:(1)在空间上,“上涌”面所造成的断层强度软化区位于隆起的边翼地区;(2)在时间上,“上涌”对构造地震的触发滞后于隆起过程。本文通过对唐山地震的分析认为,地幔物质上涌在地震孕育和发生过程中起着重要的作用,并估算了震源面上的强度软化值。最后,求出了在“上涌”作用下,地壳中所产生的最大剪切应力分布。结果表明:“上涌”造成的破裂区域最易发生在地壳中层的隆起边翼地带,而且此区域形成的断层很可能是高倾角的断层。

DISTRIBUTIONS AND CHANGES OF FAULT STRENGTH DUE TO MANTLE UPLIFT

On the basis of the mechanical interaction between elastic deformation and fluid diffusion in porous materials, this paper takes the coupled constitutive equestions as mathematical model and solves to it. The patterns and changes of additional fault strength due to mantle uplift for three types of fault have been studied. In theoretical analysis, the mechical effects to fault strength produced by the changes of pore pressure from the fluid diffusion have been taken into full account. Primary results sh ow:(1)In space, the zones of strength weakening are located in the lateral of the uplift. (2)In time, triggered time behind the process of mantle uplift.Besides, this also holds that mantle uplift may be a significant cause of the 1976 Tangshan earthquake development and occurrence through analysis. And strength weakening values have been also estimated.Finally, the patterns of maximum principal shear stress due to the uplift have been obtained. The results show that the locations of rupture occur in the sides of uplift in crust and they are likely with high dip.