| 新疆天山地区壳幔S波速度结构特征及变形分析 |
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| 引用本文： | 蔡妍, 吴建平, 明跃红, 房立华, 王未来, 孔祥艳, 杨婷, 范莉苹. 2019. 新疆天山地区壳幔S波速度结构特征及变形分析. 地球物理学报, 62(11): 4214-4226, doi: 10.6038/cjg2019M0589 |
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| 作者姓名： | 蔡妍 吴建平 明跃红 房立华 王未来 孔祥艳 杨婷 范莉苹 |
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| 作者单位： | 1. 中国地震局地球物理研究所, 北京 100081; 2. 中国地震局地震观测与地球物理成像重点实验室, 北京 100081; 3. 新疆维吾尔自治区地震局, 乌鲁木齐 830011 |
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| 基金项目： | 国家重点研发计划（2018YFC1504103），基本科研业务费（DQJB16A04）资助. |
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| 摘 要： | 天山地区地质构造复杂，地震活动频繁，其壳幔变形和深部结构一直受到学者们的高度关注.然而，由于天山地区地震台站资料较少，致使壳幔变形研究结果与解释存在诸多争议.本研究利用在天山地区（40°N-46°N，78°E-92°E）新布设的11个流动宽频带地震台站和该地区39个固定台站的观测资料，采用接收函数与面波联合反演方法，获得了研究区地壳厚度及壳幔S波速度结构.反演结果显示天山地区（41.5°N-44°N，78°E-88°E）平均地壳厚度为56 km，塔里木盆地（40°N-41.5°N，79°E-90°E）、准噶尔盆地（44°N-46°N，82°E-90°E）和吐鲁番盆地（42°N-43°N，88°E-90°E）具有较厚的沉积层，地壳平均厚度为43 km、53 km和46 km，整体表现为天山厚、盆地相对较薄的特征；在研究区南天山的最高峰（42°N，80.5°E）及北天山的最高峰（43.5°N，86°E）附近，中下地壳存在较厚的低速层，我们认为在强烈挤压作用下低速、低强度的中下地壳强烈变形可能是导致该区域快速隆升的主要原因.在研究区中部，位于塔里木盆地与准噶尔盆地之间的天山地区，中下地壳及上地幔均存在低速层，且盆地莫霍面向天山倾斜明显.结合前人的研究成果推测，在南北向构造挤压应力作用下，塔里木盆地与准噶尔盆地发生了向天山造山带方向的双向壳幔层间插入俯冲.在研究区东部，塔里木盆地东北缘与天山东部接触带的地壳内没有明显的低速层，推测应处在早期挤压变形状态，该区域的壳幔边界为缓变的速度梯度带，可能与上地幔热物质侵入或渗透有关.
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| 关 键 词： | 新疆天山地区 S波速度结构 地壳变形 联合反演 接收函数 |
| 收稿时间： | 2018-10-09 |
| 修稿时间： | 2019-02-18 |
Crust-mantle S wave velocity structures beneath Tianshan area and its deformation analysis |
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| CAI Yan, WU JianPing, MING YueHong, FANG LiHua, WANG WeiLai, KONG XiangYan, YANG Ting, FAN LiPing. 2019. Crust-mantle S wave velocity structures beneath Tianshan area and its deformation analysis. Chinese Journal of Geophysics (in Chinese), 62(11): 4214-4226, doi: 10.6038/cjg2019M0589 |
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| Authors: | CAI Yan WU JianPing MING YueHong FANG LiHua WANG WeiLai KONG XiangYan YANG Ting FAN LiPing |
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| Affiliation: | 1. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China; 2. Key Laboratory of Seismic Observation and Geophysical Imaging, Institute of Geophysics, China Earthquake Administration, Beijing 100081, China; 3. Earthquake Agency of Xinjiang Uygur Autonomous Region, Urumqi 830011, China |
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| Abstract: | Tianshan area has complex geological structures and frequent seismic activities, and its crust-mantle deformation and deep structure have been highly concerned. However, due to the lack of stations in the Tianshan area, there are still many debates about the interpretation of the crust-mantle deformation in this area. In this study, with the data of 11 new temporary stations and 39 permanent stations, we obtained the crustal thickness and the crust-mantle S-wave velocity structure beneath the study area (40°N-46°N, 78°E-92°E) by using the joint inversion of receiver function and surface wave dispersion. The results show that the average crustal thickness of the Tianshan Mountain (41.5°N-44°N, 78°E-88°E) is approximately 56 km. The Tarim Basin (40°N-41.5°N, 79°E-90°E), Junggar Basin (44°N-46°N, 82°E-90°E) and Turpan Basin (42°N-43°N, 88°E-90°E) have thick sedimentary layers, and the average crustal thickness is 43 km, 53 km and 46 km, respectively. The crustal thickness in this area is characterized by thick Tianshan Mountains and relatively thin basins. Near the highest peak of the southern (42°N, 80.5°E) and northern (43.5°N, 86°E) Tianshan Mountain, there are clear low-velocity layers in the middle and lower crust. We suggest that it is the main cause for the rapid uplift of this area that the middle-lower crust with low velocity and strength is suffered from intense deformation under the compression stress. In the central part of the study area, low-velocity zones exist both in the middle-lower crust and upper mantle beneath the Tianshan Mountain. The Moho of the Tarim Basin and Junggar Basin is both inclined to that of the Tianshan Mountain. Combined with the previous research results, it is speculated that under the north-south compression stress, the Tarim Basin and the Junggar Basin subduct and insert at different layers of the Tianshan Mountain. In the eastern part of the study area, there is no low-velocity layer in the crust of the transition zone between the northeastern margin of the Tarim Basin and the eastern Tianshan Mountain. It is speculated that the Tarim Basin and the eastern Tianshan Mountain may be in an early compression deformation stage. Besides, the crust-mantle boundary appears as a gentle velocity gradient zone, which may be related to the intrusion or penetration of thermal substances from the upper mantle. |
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| Keywords: | Tianshan area S wave velocity structure Crustal deformation Joint inversion Receiver function |
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