Crustal thickness and Poisson’s ratio beneath Zhangjiakou-Bohai seismic active belt and its neighboring regions

Based on the teleseismic events recorded by seismic stations of Shandong， Hebei， Liaoning， Beijing， Tianjin regional seismograph networks， this paper investigates the crustal thickness and average Poisson’s ratios beneath the stations by means of H-k receiver function stacking method. The results show that the crustal thickness in the studied region varies from 30 km to 46 km， and is thinning gradually from mountain to basin， suggesting a good correlation with surface terrain. On the other hand， distribution of the Poisson’s ratio over the studied region is characterized by an obvious region segmentation. The low Poisson’s ratios beneath the east part of Yanshan might relate to the delamination of North China craton. The region beneath east part of Tancheng-Lujiang fault zone exhibits a complex distribution of low Poisson’s ratios mixed with high ones， which might be related to volcanic activity. The convergence zone of the western segment of Zhangjiakou-Bohai seismic active belt and the lift exhibits a little higher Poisson’s ratios， which might be caused by both broken rocks and the partial fusion of rocks near the seismic active belt. The station Beihuangcheng located on the island chain in the Bohai Sea shows a thick crustal thickness and a low Poisson’s ratio， but the reason behind the phenomenon waits for further investigation.