Characteristics of 3D Surface Deformation Characteristics and Seismogenic Fault Inversion of 1976 Tangshan Ms 7.8 Earthquake

  Objectives  On July 28, 1976, a strong Ms 7.8 earthquake sequence occurred in Tangshan, and the influence of this earthquake continues to now.

  Methods  In order to study the deformation characteristics and seismogenic fault activities of Tangshan Ms 7.8 earthquake in 1976, we calculate quantitative results and error distribution of three-dimensional deformation before and after the 1976 Tangshan earthquake by dynamic adjustment method. And the coseismic slip distribution on the fault plane is also inversed in this paper.

  Results  The deformation results show that before the 1976 Tangshan earthquake, an overall uplift area appeares near the epicenter and the peak area of uplift which is located near Tangshan, the horizontal deformation of the epicenter area is small, and the Tangshan rhombic block rotates counterclockwise relative to the surrounding block. In the coseismic period, the Tangshan fault is dominated by right-lateral strike slip, with the vertical deformation characteristics of rising in the west and falling in the east. The inversion results show that multi-segment faults participate in the energy release of Tangshan Ms 7.8 earthquake. The distribution of seismic slip is mainly distributed in 6-18 km depth and 50 km width in the southern segment, and 7-17 km depth and 50 km width in the northern segment.The fault of Luanxian earthquake also experiences little sliding. The maximum horizontal dislocation is 7.82 m, the maximum vertical dislocation is 2.04 m, and the equivalent magnitude is Mw 7.58.

  Conclusions  The results of three-dimensional deformation field before and after the Tangshan earthquake provide valuable data for the in-depth study of the preparation and occurrence mechanism of the Tangshan earthquake and its impact.