Crustal P- and S-Wave Velocity Structure of the North China Craton at 36°N from Active-Source Seismic Data and Its Tectonic Implications

We present crustal models for seismic P-waves ( V p), S-waves ( V s) and the V p/ V s ratio across the southern North China Craton along latitude 36°N. Our results are based on inverse and forward modeling of long-range wide-angle reflection/refraction data. The crust of the southern Ordos Block has high lower crustal velocity (7.0 km/s) and a Moho depth of ∼42 km. In contrast, thick sediments and a lower average velocity (compared with the Ordos block) found underneath the Shanxi Graben are likely to be the products of rifting that has occurred since the Cenozoic. Steep Moho dips, exposed basement rock and higher average crustal velocity beneath the Lüliang Mountain and the Taihang Mountain are characteristic of an orogenic belt. The Tanlu fault and the Liaocheng-Lankao fault show sharp crustal velocity variations and a Moho offset. This seismic profile sampled the entire region of the Eastern North China Craton where the cratonic root has been destroyed and the unique crustal structure is correlated with the substantially modified lithosphere. Our crustal seismic velocity model shows a strong correspondence between surface geology, local tectonics and the deep crustal structure.