摘要
以中国西北地区的地震层析成像为基础，研究了天山地震带深部结构的基本特征．结果表明，天山地震带的地壳中部为低速的韧性滑脱层，南天山的断裂深度超过莫霍面，北天山的断裂深度一般只到地壳中部；天山莫霍面的深度一般大于５０ｋｍ，壳－幔边界由宽而缓的速度过渡带构成，中强地震主要位于盆山边界地壳中下部位波速变化较大的区域．帕米尔、南天山和塔里木之间存在一个北北东方向的低速带，乌恰和伽师地震分别位于该低速带东、西两侧的梯度带附近．推测帕米尔、南天山和塔里木之间的相对运动是导致低速带内部物质发生形变并在边界附近产生破裂的主要原因，地幔热物质的侵入对该地区的构造活动起到了重要的动力学作用．
The deep structure of the Tianshan earthquake belt is investigated,based on the seismic tomography of the northwestern China. The result indicates that a ductile detachment layer with low velocities exists in the mid-crust of the Tianshan earthquake belt; the fault in the southern Tianshan extands beyond the depth of the Moho, while the fault in the northern Tianshan only reaches mid-crust; the depth of the Moho of the Tianshan is more than 50km, moreover, the crust-mantle boundary is composed of a wide velocity transition belt. Strong earthquakes are mainly concentrated in the mid-lower crust where a sharp velocity variation is observed near the basin-mountain boundaries. A low velocity zone is found between the Pamir, southern Tianshan and Tarim, with an orientation of NNE. The earthquakes in Wuqia and Jiashi are separately located in the west and east sides of this low velocity zone. It is inferred that the relative inchon of the Pamir, southern Tianshan and Tarim is a major reason to cause deformation occurring within this low velocity zone and fracturing near its boundaries. Besides, the intrusion of hot mantle has played an important dynamic role in tectonic activities in this region.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2000年第2期184-193,共10页
Chinese Journal of Geophysics
基金
国家自然科学基金!49474214
关键词
天山
地震带
地壳结构
速度图像
伽师地震
强震
Tianshan earthquake belt, Crustal structure, Velocity image, Jiashi earthquake.
