We used episodic GNSS measurements to quantify the present-day velocity field in the northwestern Himalaya from the Himalayan foreland to the Karakoram Range. We report a progressive N-S compressional velocity gradient with two noticeable exceptions: in the Salt Range, where important southward velocities are recorded, and in Nanga Parbat, where an asymmetrical E-W velocity gradient is recorded. A review of Quaternary slip along active thrusts both in and out of sequence allows us to propose a 14 mm/year shortening rate. This constraint, together with a geometrical model of the MHT, allows us to propose estimations of the slip distributions along the active faults. The lower flat of the MHT is characterized by ductile slip, whereas the coupling increases along the crustal ramp and along the upper flat of the MHT. The basal thrust of the Potwar Plateau and Salt Range presents weak coupling, which is interpreted as the existence of a massive salt layer forming an excellent decollement. In the central part of the frontal Salt Range, the velocities suggest the existence of a southward horizontal flux in the massive salt layer. The simulations also suggest that the velocities recorded in Nanga Parbat can be explained by active westward thrusting along the fault that borders the massif to the west. Simulations suggest that the slip along this fault evolves with depth from 5 mm/year ductile slip near the MHT to no slip along the upper part of the fault.

中文翻译：

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对喜马拉雅西部构造构造下推断的断层进行量化的地震耦合

我们使用情景 GNSS 测量来量化喜马拉雅西北部从喜马拉雅前陆到喀喇昆仑山脉的当今速度场。我们报告了渐进的 NS 压缩速度梯度，但有两个明显的例外：在盐岭，记录了重要的向南速度，而在南迦帕尔巴特，记录了不对称的 EW 速度梯度。对第四纪沿活动逆冲断层滑动的回顾使我们能够提出 14 毫米/年的缩短率。这一约束与 MHT 的几何模型一起，使我们能够提出沿活动断层的滑动分布的估计。MHT 下平面以韧性滑移为特征，而耦合沿地壳斜坡和 MHT 上平面增加。Potwar 高原的基底冲断力与盐岭呈现弱耦合，解释为存在块状盐层，形成极好的脱滑作用。在锋盐岭中部，速度表明在块状盐层中存在向南的水平通量。模拟还表明，南迦帕尔巴特峰记录的速度可以通过沿着与西部地块接壤的断层向西的主动推力来解释。模拟表明，沿着这条断层的滑动随着深度从 MHT 附近 5 毫米/年的延性滑动到沿着断层上部没有滑动。速度表明在块状盐层中存在向南的水平通量。模拟还表明，南迦帕尔巴特峰记录的速度可以通过沿着与西部地块接壤的断层向西的主动逆冲来解释。模拟表明，沿着这条断层的滑动随着深度从 MHT 附近 5 毫米/年的延性滑动到沿着断层上部没有滑动。速度表明在块状盐层中存在向南的水平通量。模拟还表明，南迦帕尔巴特峰记录的速度可以通过沿着与西部地块接壤的断层向西的主动推力来解释。模拟表明，沿着这条断层的滑动随着深度从 MHT 附近 5 毫米/年的延性滑动到沿着断层上部没有滑动。