Episodicity and Rates of Thrust-sheet Motion in the Himalayas (Western Nepal)
Episodicity and Rates of Thrust-sheet Motion in the Himalayas (Western Nepal)
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喜马拉雅山脉（尼泊尔西部）的冲断面运动的偶发性和速率
DOI：
10.1306/m82813c6
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
F. Jouanne
中科院分区：
文献类型：
--
作者：
J. Mugnier;P. Huyghe;P. Leturmy;F. Jouanne
通过构造野外工作、平衡横截面、河流阶地沉积研究和大地测量学，估计了沿外带沿着单一断层和穿过尼泊尔西部喜马拉雅山整个冲断带的位移运动学和速率。GPS大地测量结果表明，该地区的缩短量为15.2mm/a，与尼泊尔喜马拉雅山脉西部的走向垂直，并与弹性应变积累相一致。这种表面缩短将引起的19毫米/年的滑动速率，在深度上，在大喜马拉雅山下的基底拆离，而拆离被锁定在小喜马拉雅山下。在外部区域，大部分的位移可能发生在重大地震事件，和2.5至5米的逆冲运动，局部观察到的叠瓦扇分支的主要逆冲的次喜马拉雅山可以反映在这些事件中的地表破裂。在全新世期间，主锋冲断层（MFT）一直很活跃，但外带的部分背驮式冲断层也显示出活动的片段，从几米到几十米的位移。MFT缩短量与喜马拉雅期总缩短量之比横向变化，从1到小于0.5不等，并且在次喜马拉雅山和可能在小喜马拉雅山发生了顺序外逆冲。这种模式的幕式序列外的再激活适合的演化的脆性逆冲楔的影响，由于断层阀的行为，表面质量运输和/或流体压力的变化。尼泊尔西部喜马拉雅山脉在中新世之后的总缩短速率为19毫米/年，而现今、全新世和长期缩短速率的不确定性分别为2、6和5毫米/年。
The kinematics and rates of displacement along single faults of the Outer Belt and through the entire thrust belt of the Himalayas of western Nepal have been estimated by structural field work, balanced cross sections, fluviatile terrace-deposit studies, and geodesy. GPS geodetic studies indicate that the shortening is 15 2mm/yr and is perpendicular to the trend of the western Nepal Himalayas and compatible with elastic strain accumulation. This surface shortening would be induced by a 19 mm/yr slip rate, at depth, on the basal detachment beneath the Great Himalayas, whereas the detachment is locked beneath the Lesser Himalayas. In the outer zone, most of the displacement presumably occurs during major seismic events, and the 2.5- to 5-m thrust movements observed locally for imbricate fans branching off the major thrusts of the Sub-Himalayas could reflect surficial rupture during these events. During the Holocene, the Main FrontalThrust (MFT) has been active, but portions of the piggyback thrusts of the Outer Belt also show episodes of activity that vary from a few meters to several tens of meters of displacement. The ratio of MFT shortening to total Himalayan shortening varies laterally, from 1 to less than 0.5, and out-of-sequence thrusting occurs in the Sub-Himalayas and possibly in the Lesser Himalayas. This pattern of episodic out-of-sequence reactivation fits with the evolution of a brittle thrust wedge affected by surficial mass transport and/or fluid pressure variation due to fault-valve behavior. The total shortening rate through the Himalayas of western Nepal following the Miocene is 19 mm/yr, with present-day, Holocene, and long-term shortening-rate uncertainties of 2, 6, and 5 mm/yr, respectively.