Study of crustal seismic velocity in the Weihe fault depression basin by seismic tomographic imaging

Abstract

This paper gives a study of 3-D crustal seismic velocity changes in the Weihe fault depression basin, in which the overlapping-sphere iterative reconstruction method of tomographic image was used in connection with the two-point fast ray tracing technique. By means of theoretical modeling, the monitoring function of the observatory network system of Shaanxi Province was tested. Using the seismic data of the network, seismic tomographic inversion imaging of the crustal seismic velocity in the Weihe fault basin was studied. The results are as follows: In the Tongchuan-Yaoxian area to the north of Jingyang, there is a high-velocity region extending nearly in NS direction, the highest velocity value is around Tongchuan. To the southwest of Shangxian and Lantian, there is a low-velocity zone about 100 km long and about 50 km wide, inside which there are two regions of the lowest velocity 50 km apart. The epicenters of historical strong earthquakes are mainly on the boundary of high-velocity regions or in regions of fairly high-velocity. In the eastern and western parts of the south margin of the Qinling Mountains, there is an obvious lateral nonhomogeneity of seismic velocity.