Study on crustal thickness and velocity ratio in mid-western North China Craton

In this study, broadband seismic records from 164 digital seismic stations of the North China Seismic Array and the China Digital Seismic Network were used to compute crustal thickness and velocity ratio (V-p/V-s) using the receiver function method and H-k stack. The results show that the crustal thickness of mid-western North China Craton deepens from east to west, the thickness is about 30 similar to 33 km in eastern plain area, 33 similar to 40 km in Yanshan-Taihangshan area and 40 similar to 42 km in Ordos block. The results also demonstrate that the correlation between the crustal average velocity ratio and the crustal thickness is not obvious, which may be related with intensive lateral variety of crustal thickness and crustal composition in the research area. The crustal average velocity ratio is about 1.68 similar to 1.86, it is mostly between 1.70 and 1.80 and changes slightly in the eastern plain area; and it is mainly between 1.70 and 1.77 in the mountain area, which suggests that the crustal composition of the mountain area has more felsic matters and lacks mafic minerals. In the research area, the relevance between the crustal thickness and the elevation is distinct, the slope is 6.6, which is higher than that in eastern Tibetan Plateau. The study results indicate that the rock density of the top of upper mantle in mid-western North China Craton is comparatively lower, and the craton is an ancient, low density, refractory craton with rich magnesium and poor iron composition, which can provide a greater buoyancy for the crust.