| 中国境内天山地壳上地幔结构的地震层析成像 |
| |
| 引用本文： | 郭飚,刘启元,陈九辉,赵大鹏,李顺成,赖院根.中国境内天山地壳上地幔结构的地震层析成像[J].地球物理学报,2006,49(6):1693-1700. |
| |
| 作者姓名： | 郭飚 刘启元 陈九辉 赵大鹏 李顺成 赖院根 |
| |
| 作者单位： | 1.中国地震局地质研究所地震动力学国家重点实验室，北京100029 2 Geodynamic Research Center, Ehime University, Matsuyama 790-8577， Japan |
| |
| 摘 要： | 根据横跨中国境内天山的库车—奎屯宽频带流动地震台阵和区域地震台网记录的近震和远震P波走时数据，利用地震层析成像方法重建了沿该地震台阵剖面下方400 km深度范围内地壳上地幔的P波速度结构.结果表明：沿新疆库车—奎屯剖面，天山地壳具有明显的横向分块结构，且南、北天山地壳显示了较为强烈的横向变形特征，表明塔里木地块对天山地壳具有强烈的侧向挤压作用；在塔里木和准噶尔地块上地幔顶部有厚度约60～90 km的高速异常体，塔里木—南天山下方的高速异常体产生了较为明显的弯曲变形，而准噶尔—北天山下方的高速异常体向南一直俯冲到中天山南侧边界下方300 km的深度，两者形成了不对称对冲构造；在塔里木和准噶尔地块下方150～400 km深度存在上地幔低速体，其中塔里木地块一侧的上地幔低速物质上涌到南天山地块的下方；在塔里木—南天山200～300 km深度范围的上地幔存在高速异常体，它可能是地幔热物质向上迁移过程融断的塔里木岩石圈的拆离体. 上述结果表明，塔里木地块的俯冲可能涉及整个岩石圈深度，但其前缘仅限于南天山的北缘；青藏高原隆升的远程效应可能不但驱动塔里木岩石圈向北俯冲，同时还造成天山造山带南侧上地幔物质的涌入；天山造山带上地幔广泛存在的低速异常有助于其上地幔的变形，而上地幔物质的强烈非均匀性应有助于推动天山造山带上地幔小尺度地幔对流的形成；根据研究区地壳上地幔速度结构特征推断，新近纪以来天山快速隆升的主要力源来自青藏高原快速隆升的远程效应，相对软弱的上地幔为加速天山造山带的变形和隆升创造了必要条件.
|
| 关 键 词： | 地震台阵 地震层析成像 地幔对流 天山造山带 |
| 文章编号： | 0001-5733（2006）06-1693-08 |
| 收稿时间： | 2006-01-10 |
| 修稿时间： | 2006-01-102006-05-22 |
Seismic tomography of the crust and upper mantle structure underneath the Chinese Tianshan |
| |
| GUO Biao,LIU Qi-Yuan,CHEN Jiu-Hui,ZHAO Da-Peng,LI Shun-Cheng,LAI Yuan-Gen.Seismic tomography of the crust and upper mantle structure underneath the Chinese Tianshan[J].Chinese Journal of Geophysics,2006,49(6):1693-1700. |
| |
| Authors: | GUO Biao LIU Qi-Yuan CHEN Jiu-Hui ZHAO Da-Peng LI Shun-Cheng LAI Yuan-Gen |
| |
| Institution: | 1.State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China 2 Geodynamic Research Center, Ehime University, Matsuyama 790-8577， Japan |
| |
| Abstract: | From the travel time data of the P arrivals recorded by the passive seismic array across the Chinese Tianshan and the regional seismic network, the P wave velocity structure of the crust and upper mantle down to 400 km along Kuqa Kuytun profile is reconstructed by using seismic tomography technique. Our results demonstrate that the crust along the profile has an obvious block structure and strong lateral crustal distortion. These manifest that the Tianshan crust is compressed strongly by the Tarim block. Beneath the Tarim and Junggar block, there are high velocity anomalies with the thickness of 60～90 km at the top of the upper mantle. The high velocity anomaly below the Tarim South Tianshan has a clear curved distortion, and that below the Junggar Northern Tianshan thrusts down to the depth of 300 km at the south side of the central Tianshan. Both of them construct an asymmetric bilateral thrusting system. Beneath the Tarim and Junggar block, in the depth range from 150 km to 400 km, exist low velocity anomalies. One of them on the Tarim side rises to bellow the south Tianshan. In the upper mantle, at the depth of 200～300 km beneath the Tarim South Tianshan, exists a high velocity anomaly, which could be the detached lithosphere of the Tarim melted by the up welling hot material of the upper mantle. All of our observations manifest that the lithosphere of Tarim block is involved in the northward subduction, but its front is limited to the north border of the south Tianshan. The long range effect caused by the uplift of the Tibetan plateau could drive not only the subduction of the Tarim lithosphere, but also the upwelling of the upper mantle in the south side of the Tianshan orogenic belt. The low velocity anomalies widely existed in the Tianshan upper mantle should facilitate the mantle deformation, and the large difference between the high and low velocity anomalies in the upper mantle may promote the small scale mantle convection. According to the crustal and upper mantle velocity structure beneath the Tianshan orogenic belt, it could be inferred that the main source driving the quick uplift of the Tianshan since Miocene comes from the long range effect caused by the uplift of the Tibetan plateau, and the relatively soft upper mantle beneath the Tianshan creates the necessary condition for accelerating the uplift and distortion of the crust. |
| |
| Keywords: | Seismic array Seismic tomography Mantle convection Tianshan orogenic belt |
| 本文献已被 CNKI 维普 万方数据 等数据库收录！ |
| 点击此处可从《地球物理学报》浏览原始摘要信息 |
| 点击此处可从《地球物理学报》下载免费的PDF全文 |
|
