| 青藏高原东南缘岩石圈有效弹性厚度及其构造意义 |
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| 引用本文： | 胡敏章,金涛勇,郝洪涛,李忠亚,王嘉沛,张勇.青藏高原东南缘岩石圈有效弹性厚度及其构造意义[J].地球物理学报,2020,63(3):969-987. |
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| 作者姓名： | 胡敏章 金涛勇 郝洪涛 李忠亚 王嘉沛 张勇 |
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| 作者单位： | 1. 地震大地测量重点实验室, 中国地震局地震研究所, 武汉 430071;2. 防灾科技学院, 河北廊坊 065201;3. 武汉大学测绘学院, 武汉 430079 |
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| 基金项目： | 国家自然科学基金面上项目（41974021），地震科技星火计划攻关项目（XH20039）资助. |
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| 摘 要： | 本文利用三维有限差分方法,基于EIGEN6C4布格重力异常和SIO V15.1地形数据,计算了青藏高原东南缘岩石圈有效弹性厚度.结果表明:青藏高原东南缘岩石圈有效弹性厚度为0~100 km,四川盆地和喜马拉雅东构造结岩石圈有效弹性厚度最大,达50~100 km;巴颜喀拉块体东部、川滇菱形块体大部、滇西等地区岩石圈强度弱,有效弹性厚度一般小于15 km;羌塘块体东部的玉树—德格附近地区岩石圈有效弹性厚度大于40 km;滇南地区岩石圈有效弹性厚度为10~30 km,大于云南北部地区.研究区域有效弹性厚度分布特征与岩石圈结构关系密切.四川盆地、喜马拉雅东构造结地区内部结构稳定,因而岩石圈强度大.川滇菱形块体等岩石圈有效弹性厚度小的地区与壳内低速、低阻/高导层分布有很好的对应关系,推测壳内岩石的部分熔融软化可能是造成高原东南缘岩石圈强度较弱的重要原因.羌塘块体东部的局部高力学强度岩石圈则可能是高原形成过程中的残留克拉通.根据本文计算的岩石圈有效弹性厚度特征,结合地震学、大地电磁等研究成果,认为青藏高原物质向东南缘挤出后受四川盆地等阻挡,造成下地壳软弱物质在理塘—稻城—丽江一带堆积,少部分物质可能穿过鲜水河断裂带的康定—道孚地区向北运动,但大部分物质向南运动,在受到滇南块体阻挡后一支流向西南的腾冲方向,另一支流向东南的攀枝花—东川方向.
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| 关 键 词： | 青藏高原东南缘 岩石圈 有效弹性厚度 |
| 收稿时间： | 2019-10-18 |
Lithospheric effective elastic thickness and its tectonics in the southeastern Qinghai-Tibet Plateau |
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| HU MinZhang,JIN TaoYong,HAO HongTao,LI ZhongYa,WANG JiaPei,ZHANG Yong.Lithospheric effective elastic thickness and its tectonics in the southeastern Qinghai-Tibet Plateau[J].Chinese Journal of Geophysics,2020,63(3):969-987. |
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| Authors: | HU MinZhang JIN TaoYong HAO HongTao LI ZhongYa WANG JiaPei ZHANG Yong |
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| Institution: | 1. Key Laboratory of Earthquake Geodesy, Institute of Seismology, China Earthquake Administration, Wuhan 430071, China;2. Institute of Disaster Prevention, Hebei Langfang 065201, China;3. School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China |
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| Abstract: | Based on the EIGEN6C4 Bouguer gravity anomaly and SIO V15.1 topographic data, the effective elastic thickness of the lithosphere (Te) in the southeastern Qinghai-Tibet Plateau is calculated by using the three-dimensional finite difference method. The results show that the effective elastic thickness of the lithosphere in the southeastern Qinghai-Tibet Plateau is 0~100 km. The Sichuan Basin and the Eastern Himalayan Syntaxes have the strongest lithosphere, and their Te is 50~100 km. The lithosphere in the eastern part of the Bayan Har Block, most of the Sichuan-Yunnan Block and Western Yunnan Block is weak, and the effective elastic thickness is generally less than 15 km; and the Te near Yushu-Dege region in the eastern part of the Qiangtang Block is larger than 40 km. The effective elastic thickness of the lithosphere in southern Yunnan is 10~30 km, which is larger than that in northern Yunnan. The distribution characteristics of effective elastic thickness in the study area are closely related to the lithospheric structure. The Sichuan Basin and the Eastern Himalayan Syntaxes have stable internal structure, so the lithosphere is strong. The low effective elastic thickness of the lithosphere, such as the Sichuan-Yunnan Block, corresponds well to the distribution of low-velocity and high-conductivity layers in the crust. It is speculated that partial melting and softening of the rocks in the crust may be an important reason for the weak strength of the lithosphere in the southeastern Plateau. The local high mechanical strength lithosphere in the eastern part of the Qiangtang Block may be a residual craton in the process of Plateau formation. According to the characteristics of effective elastic thickness of lithosphere calculated in this paper, combined with the research results of seismology and magnetotellurics, it is considered that the material of Qinghai-Tibet Plateau is blocked by Sichuan Basin after extrusion to the southeastern margin, which results in the accumulation of soft material in the lower crust along Litang-Daocheng-Lijiang area. A small part of the material may move northward through Kangding-Daofu area of Xianshuihe fault zone, but most of the material moves southward. After being blocked by the South Yunnan Block, one branch flows to Tengchong in the southwest and the other to Panzhihua-Dongchuan in the southeast. |
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| Keywords: | Southeastern Qianghai-Tibet Plateau Lithosphere Effective elastic thickness |
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