Velocity structure tomography analysis in southern Hebei Province

Abstract

The destruction of cratons is one of the key research objects of geophysicists. According to China Earthquake Networks Center, small and medium-sized earthquakes have occurred more frequently in southern Hebei in recent years than before. In order to explore the reasons for the instability of the crustal structure in southern Hebei, in this paper the earthquakes are precisely located based on the P-wave arrival time data recorded by China Earthquake Networks Center, and the double difference tomography of the crustal velocity structure is performed by using the P-wave seismic phase data. It is found that the sources after fine location are mainly distributed in the crust depth of 5～15 km, mainly near the faults. In terms of velocity structure, the mean RMS value of seismic travel time residuals decreases from 0.81 s to 0.36 s, and the earthquakes are more likely to occur in the transition zone at the edge of the high-speed region. There is a low-speed anomaly zone at the junction of the crust and mantle in Handan and Xingtai. The Moho surface and upper mantle may be upwelling by hot flow materials such as magma, intruding into the crust and undergoing chemical reactions, leading to the thinning and damage of the lithosphere, resulting in an unstable crustal structure and creating favorable conditions for shallow earthquakes.

Keywords

• double-difference tomography
• lithosphere destruction
• three-dimensional velocity structure
• southern hebei