Velocity Structure of The Upper Crust and Its Geological Significance In Northwest Shandong Province, China

Northwest Shandong Province (NSP) is located in the eastern part of the North China Plate, which contains several intraplate extensional structures, such as the Jiyang depression and the northern part of the Luxi uplift. At present, analysis of the crustal velocity structure in this area is mainly based on artificial seismic methods, and high-resolution three-dimensional velocity structure results are lacking. Study on the upper crustal structure and structural characteristics have not been comprehensive or detailed. The high-resolution three-dimensional crustal velocity structure in NSP would be helpful for in-depth analysis of the crustal structure characteristics in this area, and of great significance to interpreting the deep structural characteristics of the secondary uplift and depression structural units in the area. Therefore, we obtained the velocity structure of the upper crust in NSP using double-difference seismic tomography, and found that the crust in the near-surface area of the depression structure presents an obvious low velocity layer with large scale and great depth, which is related to the relatively thick loose sediments in the depression area. The structure of the Luxi uplift to the south of the Qihe–Guangrao fault shows an obvious high velocity anomaly, which is related to the overall uplift of the crust and upwelling of mantle materials. The Chengning uplift, Binzhou uplift, Qingcheng uplift, Guangrao uplift, and Shouguang uplift to the north of the Qihe–Guangrao fault do not show obvious high velocity anomalies near the surface, but there are upward high-velocity structures beneath these uplifts. The uplift structures to the north of the Qihe–Guangrao fault were formed on the basis of the overall subsidence of the Jiyang depression and are typical, whereas the structure of the Luxi uplift was characterized by overall uplift.