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 away from plate margin, developed a very typical fold-and-thrust system, and its deep structural and tectonic features reflect the crustal shortening and deformation processes in the intra-continental environment. This study, using the three-component teleseismic waveform data recorded on the Hefeng seismic station in Hubei province within the Wuling fold belt, we extracted the receiver function and focused on analyzing the characteristics of the change in back azimuth of the Ps converted seismic phases with the teleseismic event, which revealed the differences in crustal structure between the two sides of the Hefeng fault. The key findings are as follows: the difference between the Ps and the direct P arrival time is about 4.5 s for the SE-directed event, while the difference between the Ps and the direct P arrival time is about 5.5 s for the W and NE 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 analysis show that there is a sharp contrast in the crustal thickness on both sides of the Hefeng fault, which is steeply increased from 30 km on the east side to about more than 40 km on the west side, and there is an obvious velocity discontinuity on the west side of the Hefeng fault. These findings may offer new constraints for a deeper understanding of the dynamic mechanisms and processes of intra-continental deformation in the Wuling Mountains.