晋冀蒙交界地区的地壳厚度与泊松比特征

Characteristics of Crustal Thickness and Velocity Ratio at the Junction of Shanxi, Hebei and Inner Mongolia

根据晋冀蒙交界地区固定台和流动台共计78个台站记录的高质量远震资料,得到了共计6978个接收函数,反演了晋冀蒙交界地区的地壳厚度与波速比结果。结果显示,研究区的地壳厚度在31~45 km,变化幅度较大,具有由东向西逐渐加厚的横向变化,并且沿着东南-西北方向有渐变特征。台站下方地壳速度比在1.63~1.90,对应的泊松比在0.18~0.31,具有明显的分块特征。波速比相对较高的地区多为沉积盆地断陷中心地带及附近区域,波速比较低的区域分布在太行山脉中段与吕梁山地区等隆起区域附近。大同火山区波速比高于周边地区,是火山剧烈活动引起地幔物质上涌的反映。太行山山前断裂带附近的台站下方地壳平均速度比呈现由北向南逐渐减小的特征,表明此区域地壳分层结构明显,同时也反映了平原地区与山脉地区的地壳介质成分的差异。

Based on the high-quality teleseismic data recorded by 78 stations in the fixed and mobile stations in the border area of Shanxi, Hebei and Inner Mongolia, a total of 6978 receiver functions were obtained, and the crustal thickness and wave velocity ratio were calculated in the research area. The results show that the crustal thickness of the study area is between 31 km and 45 km, and the variation span is large. It gradually thickens from east to west and exhibits graded property along the southeast-northwest direction. The crustal velocity ratio below the stations is between 1.63 and 1.90, and the corresponding Poisson’s ratio is 0.18 to 0.31. The velocity ratio has obvious block characteristics. The relatively high values mostly distribute in the central zone of the sedimentary basins and their vicinity. The lower values are located in the middle of the Taihang Mountain and the Lüliang Mountain area. The wave velocity ratio of Datong volcanic area is higher than that of the surrounding area, illustrating the upwelling of mantle materials caused by the violent activity of the volcanos. It is characterized that the average velocity ratio of the crust below the stations at the Taihang Mountain fault zone gradually decrease from north to south, which indicates the obvious layered crustal structure in this area, and the difference of crustal medium composition between the plain and the mountain regions.