N: 0cm 0cm 0pt" class=MsoNormal>nzhang>na; FONT-SIZE: 10pt" lang=EN-US>The authors use the three-dimensional non-linear dynamic finite element method to perform a modeling study on dynamical stress effects with a rhombic model and analyze the Tangshan na; FONT-SIZE: 10pt" lang=EN-US>Mnzhang>na; FONT-SIZE: 10pt" lang=EN-US>7.8 Earthquake in 1976. The result shows that stress wave is generated by shock force before the Tangshan earthquake, when this wave encounters a fault, the reflected stress wave, becomes tensile due to half-wavelength loss, which causes cracks, local rupture and crack linkage in the rock by reducing rock friction. On the one hand, other earthquakes are triggered. On the other hand, energy for the namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />