中国西北地区剪切波三维速度结构

本文研究区包括中国西北地区几个不同的构造单元,即准噶尔、阿尔泰、天山、内蒙古褶皱、塔里木盆地、柴达木和祁连山地区.从群速度和剪切波速度模型上可以看出,除塔里木具有十分明显的稳定构造体特征外,其它地区均具构造活动地区的特征,但其速度表现各具特点,并与它们的构造演化史有关.莫霍界面的起伏基本上控制了布格重力异常的分布;另外,天山地区与北山的速度结构在土地幔盖层中差别很大,天山的上地幔高速盖层可能与应力场有关.

3-D SHEAR VELOCITY STRUCTURE IN NORTH-WEST CHINA

Different tectonic units in North-West China, such as Junggar Basin, Altay Mt., Tian-shan Mt., Inner-Mongolian Fold Zone, Tarim Basin, Qaidam Basin and Qilian Mt., are discussed in the present study. It is found out based on the group velocity of Rayleigh wave and the relevant models of shear wave velocity in depth that Tarim Basin shows certain distinct features of a stable geological block, while other tectonic units belong to active areas. Their particular velocity distribution in depth are related to their tectonic evolution. A considerable portion of Bouguer gravity anomaly is contributed by the relief of Moho discontinuity. It is also found out that there exist obvious difference in velocity structure between eastern part （Beishan） and western part of Tianshan in the lid of the upper mantle. The high velocity lid in the upper mantle is related to the special stress field in this area.