新疆地区S波分裂研究

Shear wave splitting in Xinjiang region

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,采用最小能量法和旋转相关法分别对SKS、SKKS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).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之间.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,表明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,表明该断裂已经切穿整个岩石圈.

Shear wave splitting analysis has been carried out using teleseismic data from broadband digital seismic stations permanently deployed in Xinjiang region.We determined fast polarization direction（φ） and delay time（δt） between fast and slow waves using both the minimum energy method and rotation-correlation method.Our measurements show that fast directions of teleseismic shear wave beneath the northern Tarim basin,Tien Shan orogenic belt and Altai orogenic belt are generally parallel to the strike of structure beneath the stations.The delay times vary from 0.8 s to 1.8 s.All of these are related to shortening of lithosphere caused by the collision between India and Eurasia continent.In contrast,weak anisotropy beneath Tarim basin and Junggar basin implies that these basins have not experienced strong deformation since Cambrian.The fast polarization directions near the Altyn fault show remarkable correspondence with the fault strike,indicating that the fault may cut the whole lithosphere.