Crustal structural variations around the Hefeng fault: Implications from teleseismic receiver function study on the Hefeng seismic station

The Wuling fold belt, located on the western part of the South China continent, far from the plate margin, has developed a typical fold-and-thrust system and its deep structural and tectonic features reflect the crustal shortening and deformation processes in the intra-continental environment. Using the three-component teleseismic waveform data recorded at the Hefeng seismic station in Hubei Province within the Wuling fold belt, we extracted the P-wave receiver functions and focused on analyzing the characteristics of the change of Ps phase in back azimuth of teleseismic events, which revealed the differences in crustal structure between the two sides of the Hefeng fault. The key findings are as follows: the difference in arrival times between Ps phase and the direct P wave was about 4.8 s for the SE-directed events, whereas it was about 5.5 s for the NW-directed events. The significant difference in the arrival times of the Ps phases reflects that the Hefeng fault is a regional fault that extends to the depth of the Moho. CCP imaging and H-κ scanning analyses revealed a sharp contrast in the crustal thickness on the two sides of the Hefeng fault, which is steeply increased from 30 km on the SE side to about more than 40 km on the NW side, and there is an obvious intra-crustal velocity discontinuity on the NW side of the Hefeng fault. These findings offer new constraints for further studies on the dynamic mechanisms and processes of intra-continental deformation in the Wuling Mountains.