Crustal structure of the northern margin of north China craton from Huailai to Sonid Youqi profile

The SinoProbe-02 North China joint seismic experiment consisted of three seismic recording efforts along 453 km long profile. The profile extended from the Huailai basin, across the Yinshan-Yanshan belt, Inner Mongolia paleo-uplift, Bainaimiao arc, Ondor Sum accretion complex to the Solonker suture zone. We processed, analyzed, and modeled the data collected during the wide-angle reflection and refraction effort. The seismic waves from 8 explosions were recorded by 300 Texan recorders. The P-wave field provided good quality data for most of the profile. Arrivals of refracted and reflected waves from sediments and basement (Pg), intracrustal phases (PcP, PIP), and the Moho (PmP, Pn) were typically observed. Hole's first arrival tomography program was used to obtain the upper crustal velocity structure. And Zelt's 2D travel time raytracing and inversion program (Rayinvr) was used to obtain the full crustal structure. The final 2D P-wave velocity model contains many features of tectonic significance: (1) The flat and relatively shallow Moho in the Central Asia Orogeny Belt (CAOB) may be attributed to the extension; thicker crust appears beneath the Yinshan-Yanshan belt and was probably generated by compression in the Jurassic-Cretaceous and modified during the later extension; (2) The velocity structure varies significantly from the NCC to the CAOB, and the boundary between them appears at the Chifeng-Bayan Obo fault; (3) Relatively high velocities in the upper crust of the middle part of the profile may represent the outcrop of large area granites; strong velocity variations beneath the Bainaimiao arc and Ondor Sum subduction accretion complex indicate that multiple pulses of magmatism occurred during the complex tectonic evolution, of this area.