Lithospheric rheology and Moho upheaval control the generation mechanism of the intraplate earthquakes in the North China Basin

• Large earthquakes occurred in the regions where Moho upheaves in the NCB.
• Interseismic crustal stress accumulation is simulated under the condition of compression.
• Stress concentration in the regions where Moho upheaves is responsible for the earthquakes.
• Both lithospheric rheology and Moho upheaval control the stress accumulation process.

Many devastating intraplate earthquakes, such as the 1966 Xingtai earthquake (Ms 7.2) and the 1976 Tangshan earthquake (Ms 7.8), occurred in the North China Basin (NCB). This study aims to investigate the generation mechanism of the large intraplate earthquakes in the NCB and the spatial distribution of earthquake activity through numerical experiments. In order to simulate the interseismic stress accumulation process in the NCB, we set up several 3D finite element models based on different lithospheric rheological structure and apply boundary conditions of horizontal compression. We find that stress concentration with high rate in the regions where Moho upheaves is responsible for the large earthquakes in the NCB. During the interseismic period large stress rate is located nearly around the bottom of the brittle upper crust, where stress accumulates fast to reach fault strength and active the main shocks. Aftershocks in the seismogenic layers could be triggered by the main shocks. Two factors are critical to the crustal stress accumulation process. (1) The first is Moho upheaval in the seismic zones. (2) The second is viscosity contrast among the crustal layers. Our results support the lithospheric rheological structure in the NCB as following: the brittle upper crust, brittle–ductile transition in the middle crust, the ductile lower crust, and the ductile lithospheric upper mantle.