Present crustal deformation and stress-strain fields of North China revealed from GPS observations and finite element modelling

摘要

North China is located on the N-S seismic belt of mainland China and is characterized by dense faults and intense seismicity. We analyzed the current regional crustal deformation using GPS observations from 1999 to 2007 and 2011-2017. We then established a dynamic finite element model based on the geological structure, geophysical parameters, and GPS velocity constraints to analyze the strain-stress features. Finally, we discuss the rationality of the simulation results, the variations in crustal activity, which may have been caused by the post-earthquake impact of the 2011 Mw 9.0 Tohoku and 2008 Mw 7.9 Wenchuan earthquakes, and the geodynamics of North China. Most parts of North China exhibited extensional stress in an approximately NW SE direction during 2011-2017. In the two study periods, the maximum shear strain rates predominantly occurred in western North China; the central and eastern parts had relatively smaller values in 2011-2017. These characteristics indicate that the post-earthquake impact of the Tohoku earthquake significantly influenced most parts (central and eastern) of North China, whereas the Wenchuan earthquake mainly affected the western part. Our work quantitatively described the variations in current crustal movement velocities, stress-strain fields, and fault activity rates in North China. These characteristics indicate that the unique tectonic environment, intense crustal activity, and earthquake-prone nature of North China require continuous research attention. The results obtained in this study not only portray the current tectonic activity deformations but also reveal recent geodynamic processes in North China.