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.