【作者】 冯强强；

【导师】 吴庆举； 李永华；

【作者基本信息】 中国地震局地球物理研究所 ， 地球探测与信息技术， 2011， 硕士

【摘要】 研究表明地球内部不同内部圈层的结构和构造在本质上是不均匀和各向异性的,因此我们可以通过各向异性反演地球内部的结构,从而推断研究区现今和过去内部演化过程的应变场状态及地球内部物质的变形特征。对地球内部各向异性的研究已经成为地震学研究的一项重要内容。新疆地区构造复杂,地震活动性强,区内分布着许多巨型的造山带和巨型断裂带,是研究陆内造山带和印度-欧亚板块碰撞远程效应的天然试验场,也是目前全球地质、地球物理研究的热点之一。本文采用剪切波分裂方法,研究了新疆地区地壳上地幔的各向异性。本文主要开展了以下几方面的研究：总结了地震各向异性研究的历史与现状,概况了前人在研究区域做的工作和已经获得的关键性认识；以横向各向同性介质为例,分析了地震波在各向异性介质中的传播规律,并且阐述了剪切波分裂的原理；对目前常用的剪切波分裂测量方法进行了分析比较；最后,本文利用国家地震台网及中国地震局“十五”期间在新疆地区布设的宽频地震台站记录到的远震波形数据,分别采用最小能量法和旋转相关法对SKS、SKKS波震相进行了偏振分析,计算了台站下方介质各向异性的分裂参数：快波的偏振方向(φ)和慢波延迟时间(δt)。本文研究结果表明,塔里木盆地北缘、天山造山带和阿尔泰造山带大多数台站的快波偏振方向与台站下方构造走向方向接近,其快慢波分裂延迟介于0.8～1.8s,这与印度-欧亚碰撞导致的岩石圈缩短有关。相比而言,塔里木盆地和准噶尔盆地内部的各向异性强度明显要弱,暗示其自前寒武形成以来并没有经历强烈的变形作用。阿尔金断裂带附近台站下方各向异性快波方向与断裂带的走向具有很强的相关性,暗示该断裂已经切穿整个岩石圈。更多还原

【Abstract】 The Xinjiang has undergone a complex tectonic evolution, being affected by the collision of Indian and Eurasian that is expected to left some imprints on the crust and mantle. Xinjiang is generally divided into four major tectonic regions:tienshan orogenies, Tarim basin, Junggar basin, and Altai orogenies. This region is and is characterized by the presence of large-scale, NEE-SWW trending thrust faults and associated earthquakes and is a key place for understanding the basic questions of continental dynamics.In this paper, we overviewed the progresses and achievements on the seismic anisotropy. We examined in detail the example of plane waves propagating an anisotropy media with hexagonal symmetry and explained the occurrence of shear wave splitting. We also compared sensitivity and reliability of three basic techniques of shear-wave splitting analysis. Shear wave splitting analyses have been carried out using teleseismic data from broadband digital stations permanently deployed in Xin Jiang region, we determined fast polarization direction ((?)) and delay time (<δt) between the fast and slow waves using both the minimum energy method and rotation-correlation method.Our measurements show that fast directions of teleseismic shear waves beneath the northern Tarim basin, Tien Shan orogenic belt and Altai orogenic belt are generally parallel to the strike of the structure beneath the stations respectively. Delay times vary from 0.8s to 1.8s. All of these are related to shorten of lithosphere caused by the collision between India continent and Eurasia continent. In contrast, weak anisotropy beneath Tarim Basin and Junggar Basin implies that these Basins had not experienced strong deformation since Cambrian. The fast polarization direction near the Altyn fault corresponds to the strike of the fault which implies the fault had cut the whole lithosphere.更多还原