Structural characteristics of Yanyuan basin deduced from seismic survey and its dynamic implication

In this paper, an artificial seismic line and a short period natural seismic array covering Yanyuan basin are set up. The seismic energy attribute is extracted from the artificial seismic data, and the seismic velocity structure is obtained by seismic tomography. Meanwhile the S-wave velocity distribution at different depths is obtained by inverting the empirical Green’s functions retrieved from cross-correlation of the ambient noise data recorded by the short period seismic array. The results show that Yanyuan basin is mainly divided into three layers by seismic characteristics. The shallow layer is the Cenozoic sedimentary stratum with low P wave velocity ranging from 1.0 km/s to 2.1 km/s, and it is characterized by good continuity and strong reflection. The S wave velocity is low in the south and high in the middle of Yanyuan basin, and the trend of the low-velocity anomaly in the south is in agreement with the strike of Yanyuan fault. Cenozoic basin is thick in the south and thin in the north, where the sedimentary and structure are controlled by Yanyuan fault. The middle layer is medium-low P wave velocity ranging from 3.5 km/s to 4.5 km/s, and it is characterized by discontinuous reflection axis and weak reflection, which can be interpreted as Triassic strata. The S-velocity becomes higher gradually and the change becomes smaller in general. The deep layer is high velocity, characterized by chaotic seismic reflection and weak reflection energy, interpreted as Paleozoic strata. Furthermone, there is a detachment surface in the upper crust, which is the interface between sedimentary and basement. A series of faults are developed from the detachment to the surface, and these faults are also an earthquake-prone area in Yanyuan basin. One of the faults is Jinhe-Qinghe fault, which is the boundary fault between Yanyuan basin and Kangdian block.