Numerical modelling of stress fields and earthquakes jointly controlled by NE- and NW-trending fault zones in the Central North China Block

• The stress concentration regions are all located at the transition zones between two group of faults.
• The distribution of the stress field after large earthquakes are dominated by two group of faults.
• The geometry of the main faults control the stress field and earthquakes distribution.

The stress field of the Central North China Block (CNCB) has been affected by the interaction among the Indian, Eurasian and Pacific Ocean plates, and the effect is manifested by the occurrence of large earthquakes in this region. Here, using numerical simulation of the finite element method, attempts were made to evaluate ESE-directed compression on three tectonic zones, namely, the Shanxi Graben Zone, the Zhangjiakou-Penglai Fault Zone and the Taihangshan Fault Zone. In these zones, the structural geometry and viscoelastic property of the model were determined, as well as 49 main faults identified, by means of a comprehensive structural analysis of seismic profiles, gravity data and tomography. This study shows that the stress concentration areas in the three zones are all located in the transition zone between NE-trending and NW-trending faults. Numerical simulation analysis of the Xingtai and Tangshan earthquakes revealed that the NE- and NW-trending faults had played an important role in controlling the distribution of the stress field, triggering aftershocks and/or stopping stress propagation during earthquakes. The differences of the stress fields and earthquake distributions among the three tectonic zones resulted from not only the fault combination patterns, but also the geometry of the main faults.