天山构造带及邻区地壳各向异性

天山构造带位于中国大陆西北部，是典型的岩石圈陆内缩短造山带.本文利用新疆区域数字地震台网2009年1月至2014年12月的近场小地震波形资料，采用剪切波分裂分析对天山构造带及邻区的地壳各向异性特征进行研究，获得了研究区域内39个台站的快剪切波偏振方向和慢剪切波时间延迟.剪切波分裂参数的空间特征显示，研究区上地壳各向异性具有分区性，各向异性特征与局部构造、地壳介质变形和应力分布有关.天山构造带的快剪切波偏振呈现出两个优势方向的特点，第一优势方向大致平行于台站附近断裂和天山构造带的走向，与断裂构造和应力的综合影响有关，另一个优势方向反映了主压应力的直接作用.北天山山前断裂带东段的断裂弯折部位和南天山局部地区的剪切波分裂参数与东、西两侧不同，与准噶尔盆地、塔里木盆地的南北向挤压作用密切相关.快剪切波偏振优势方向的剧烈变化揭示，在准噶尔盆地和塔里木盆地双向挤压隆起的过程中，天山构造带产生了强烈的局部不均匀变形.塔里木盆地西侧快剪切波偏振具有两个优势方向，一个为NNE方向，与帕米尔高原受到印度-欧亚板块碰撞产生的北向挤压作用有关，另一个为NW方向，指出了塔里木盆地区域主压应力方向.准噶尔盆地北部也存在NE和NW两个快波偏振优势方向，主要与断裂的影响有关.天山构造带区域内的慢剪切波时间延迟总体上低于塔里木盆地西侧和准噶尔盆地北部，同时慢剪切波时间延迟的结果也进一步证实了天山构造带的局部强烈变形.

Crustal seismic anisotropy in the Tien Shan and adjacent areas

The Tien Shan tectonic belt is located in northwest of the mainland China, which is the typical lithosphere intercontinental shortening orogenic belt. In this study, the parameters of anisotropic characteristics of the 40 stations are computed with the systemic analysis method of shear-wave splitting based on the seismic data during January 2009 to December 2014, recorded by Xinjiang Regional Digital Seismic Network. The spatial characteristics of shear-wave splitting parameters demonstrate obvious zoning of anisotropic in the upper crust, anisotropic characteristics are related to local structures, crustal medium deformation and stress distribution. There are two polarizations of fast shear-waves in the Tien Shan tectonic belt, of which the first dominant polarization is generally parallel to the fault strike nearby the stations and the strike of the Tien Shan tectonic belt, which is related to the fault structures and stress; the second predominant polarization reflects directly the effect of compressive stress. The shear-wave splitting parameters of the east bending part of the North Tien Shan piedmont fault and local part of South Tien Shan piedmont fault are closely related to the two-way extrusion from Tarim Basin and Junggar Basin. The acute changes of predominant polarization indicate the local inhomogeneous deformation. The west side of Tarim Basin shows two directions, one is NNE, which is related to the northward compression of Pamirs caused by India-Eurasia collision, and the other indicates the direction of the compressive stress of Tarim Basin is NW. The NE and NW polarizations of fast shear-wave in Junggar Basin are related to the faults. The time delay of shear waves in the Tien Shan tectonic belt is generally below the time delay in Tarim Basin and Junggar Basin, and the results further demonstrate intense local deformation in the Tien Shan tectonic belt.