中国北部及其邻区地壳上地幔三维速度结构

3D S-WAVE VELOCITY STRUCTURC OF CRUST AND UPPER MANTLE IN THE NORTHERN CHINA AND ITS ADJACENT AREAS

本文利用中周期和长周期瑞利面波资料分别反演得到中国北部及其邻区的三维Ｓ波速度结构．结果表明，地壳中横向非均匀性非常明显，许多地区显示出构造活动的特征；上地幔速度结构的横向变化相对减小．研究区的地壳厚度从东向西逐渐增大，地壳平均速度分布的格局与地壳厚度分布大体一致．地壳厚度与地壳平均速度的突变带处与布格重力异常梯级带基本一致．从数据上看，地壳厚度远比地壳平均速度与布格重力异常的一致性程度高，因此可以确定莫霍界面的起伏是控制布格重力异常的主要因素．

In this paper,an inversion has been made of 3D S-wave velocity structure of crust and upper mantle in the northern China and its adjacent areas from long and middle period Rapleigh wave data respectively.The results show that the lateral inhomogeneity is very evident in crust,the characteristics of the active tectonics areshown in many district,but the leteral change of uppe mantle velocity structure has been lessened relatively.The crustal thickness In the studied region increases gradually from eastto west.The crustal average veloclty distribution framework corresponds with the distribution of the crustal thickness.The abrupt variation belt of crustal thickness and average velocity are basically identical with the distribution tendency of gradient belts of Bouguergr avity anomaly.From the value variation,the identity of Bouguer gravity anomaly and crustal thickness distribution is much higher than that of gravity anomaly and average velocity.Therefore,we candetermine that the fluctuation of Moho discontinuity is the main factor controlling Bouguer gravity anomaly.