Coseismic and contemporary deformation features of the M_S7.8 Tangshan earthquake in 1976

This paper analyzed the coseismic rupture parameters, distribution of coseismic strain release and contemporary strain accumulation features based on coseismic displacements and GPS velocities in source area of the M_S7.8 Tang-shan earthquake in 1976. The fitting results for the dislocation formula in two-dimensional model of coseismic displacements show that the locking depth of seismic fault is about 18—23 km before Tangshan earthquake, its dip angle is about 74°—90°, and the coseismic dislocation is about 3.1—3.4 m. During the coseismic process, right-lateral rupture occurred in the Tangshan fault zone, and the left-lateral strain released in NE direction at the bilateral sides of the coseismic fault. On the condition of the density and accuracy of GPS surveying presented in this paper, the creep signal cannot be distinguished at present. The coseismic strain release and contemporary GPS strain rate accumulation results illustrate that the shearing deformation (rate) magnitude in the SE side of the Tangshan fault zone is larger than that in the NW side, and the deformation values between the coseismic process and contemporary period differs 1000 times.