Velocity structure of the upper crust beneath the Jiaonan uplift and its adjacent areas, China

Abstract

The Jiaonan uplift and its adjacent areas (JUAA) are the result of collision and amalgamation of the North China plate and Yangtze plate. In this area, the tectonic environment is complex and crustal deformation is strong. However, detailed and in-depth study of the upper crustal structure and medium properties in the JUAA has not previously been performed. The high-resolution three-dimensional crustal velocity structure of the JUAA is helpful to analyze the characteristics of the crustal structure in this area and is important for evaluating the tectonic environment and medium properties of the JUAA. We obtained the three-dimensional crustal velocity structure in the JUAA using the double-difference seismic tomography technique, and found that the Rizhao area and the sea areas to its southwest in the Jiaonan uplift are characterized by a high-velocity structure, and that most of the high-velocity anomaly area is located in the sea area. The crustal velocity values of the southern end of the Yishu fault zone are also high. The high crustal velocity anomaly areas in the JUAA are considered to be caused by the upwelling of mantle material. The velocity structure of the upper crust beneath the depression structures shows notable low-velocity anomalies, which are closely related to loose sediments in the depression structures. The existence of abnormally high-velocity and low-velocity structures in the Jiaonan uplift indicates that there are substantial differences in the properties of the crustal media in the Jiaonan uplift. Crust-mantle interaction in the Jiaonan uplift is mainly concentrated in the Rizhao area and sea areas to its southwest.