Late Quaternary vertical slip rates along the Southern Yadong-Gulu Rift, Southern Tibetan Plateau
Late Quaternary vertical slip rates along the Southern Yadong-Gulu Rift, Southern Tibetan Plateau
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藏南高原亚东-古鲁裂谷南部晚第四纪垂直滑移速率
DOI：
10.1016/j.tecto.2019.02.014
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发表时间：
2019
期刊：
影响因子：
2.9
通讯作者：
Liu Feng
中科院分区：
文献类型：
--
作者：
Ha Guanghao;Wu Zhonghai;Liu Feng
亚东-古鲁裂谷是典型的北向裂谷，但其南段的垂向滑动速率缺乏定量资料。南亚东-古鲁裂谷由热龙、涅鲁和帕格里-多青三处地堑组成，受其东部边界正断层控制。为了确定垂直滑动速率，我们测量了沿主断层道断层陡坡的平均高度，并用光学激发发光（OSL）测年法测定了被断层陡坡位移的沉积物年代。结果表明，这些断崖年龄集中在晚更新世，垂向间距约为5.5 ~ 22 m。后放弃明显不准确的位移,我们估计的平均垂直滑动率Relong地堑是0.7 ±0.1 0.8毫米/年和Nieru地堑 ±0.1 毫米/年,而Pagri-Duoqing有限地堑是2.0 ±0.5 毫米/年以来最新的第四纪(ca。15 ka)加权平均滑动速率与误差。认为不同的滑动速率源于涅尔和热龙地堑周围其他断裂的分散变形，以及下地壳和北喜马拉雅片麻岩穹丘内部的韧性变形。此外，与亚东-古鲁裂谷北部相比，历史文献中缺乏大地震记录，推断出的地震迁移模式和对北上裂谷的MHT触发，共同表明亚东-古鲁裂谷南部可能是中-大地震的高风险地区（M ≥ 6）。
Determination of vertical slip rate on different timescales is one of the critical issues along north-trending rifts in Southern Tibet. The Yadong–Gulu rift, a typical example of these north-trending rifts, lacked sufficient quantitative data about the vertical slip rate along its southern portion. The southern Yadong–Gulu rift is comprised of the Relong, Nieru and the Pagri–Duoqing Co grabens, which are controlled by a normal fault along its eastern boundary. To determine the vertical slip rate, we measured the average height of fault scarps along the main fault trace and dated sediments displaced by the scarps by Optically Stimulated Luminescence (OSL) dating. The results indicated that the ages of these fault scarps clustered at late Pleistocene, and the vertical separation of scarps ranged from about 5.5 m to 22 m. After abandoning distinctly inaccurate displacements, we estimate that the average vertical slip rate of Relong graben is 0.7 ± 0.1 mm/yr and Nieru graben is 0.8 ± 0.1 mm/yr, while that of Pagri–Duoqing Co graben is 2.0 ± 0.5 mm/yr since the latest Quaternary (ca. 15 ka) by weighting mean slip rate with error. It is considered that the different slip rates derive from the dispersed deformation of other faults around the Nieru and Relong graben and ductile deformation within the lower crust and northern Himalaya gneiss dome. Besides, the lack of large earthquakes in historical documents compared with the northern part of Yadong-Gulu rift, the inferred pattern of seismic migration and triggering of MHT to north-trending rifts, together indicate that the southern Yadong–Gulu rift is at high risks for middle to large earthquakes (M ≥ 6) possibly.