In this study, we use published geologic maps and cross-sections to construct a three-dimensional geologic model of major shear zones that make up the Himalayan orogenic wedge. The model incorporates microseismicity, megathrust coupling, and various derivatives of the topography to address several questions regarding observed crustal strain patterns and how they are expressed in the landscape. These questions include: (1) How does vertical thickening vary along strike of the orogen? (2) What is the role of oblique convergence in contributing to along-strike thickness variations and the style of deformation? (3) How do variations in the coupling along the megathrust affect the overlying structural style? (4) Do lateral ramps exist along the megathrust? (5) What structural styles underlie and are possibly responsible for the generation of high-elevation, low-relief landscapes? Our model shows that the orogenic core of the western and central Himalaya displays significant along-strike variation in its thickness, from ∼25–26 km in the western Himalaya to ∼34–42 km in the central Himalaya. The thickness of the orogenic core changes abruptly across the western bounding shear zone of the Gurla Mandhata metamorphic core complex, demonstrating a change in the style of strain there. Pressure-temperature-time results indicate that the thickness of the orogenic core at 37 Ma is 17 km. Assuming this is constant along strike from 81°E to 85°E indicates that, the western and central Nepal Himalaya have been thickened by 0.5 and 1–1.5 times, respectively. West of Gurla Mandhata the orogenic core is significantly thinner and underlies a large 11,000 km2 Neogene basin (Zhada). A broad, thick orogenic core associated with thrust duplexing is collocated with an 8500 km2 high-elevation, low-relief surface in the Mugu-Dolpa region of west Nepal. We propose that these results can be explained by oblique convergence along a megathrust with an along-strike and down-dip heterogeneous coupling pattern influenced by frontal and oblique ramps along the megathrust.

中文翻译：

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弧形造山楔中的三维应变累积和分配：以喜马拉雅山为例

在这项研究中，我们使用已发布的地质图和剖面图来构建构成喜马拉雅造山楔的主要剪切带的三维地质模型。该模型结合了微震性，大推力耦合以及地形的各种派生形式，以解决有关观测到的地壳应变模式及其在地形中如何表达的几个问题。这些问题包括：（1）垂直增厚如何随着造山带走向而变化？（2）倾斜会聚在导致沿走向厚度变化和变形方式方面有什么作用？（3）沿大推力的耦合变化如何影响上覆的构造样式？（4）沿大推力是否存在横向斜坡？（5）生成高海拔，低浮雕景观的基础是哪些结构风格？我们的模型显示，喜马拉雅西部和中部的造山带厚度沿走动方向变化很大，从喜马拉雅西部的〜25-26 km到喜马拉雅中部的〜34-42 km。整个古拉Mandhata变质岩心复合体的西部边界剪切带的造山岩心厚度突然变化，证明那里的应变方式发生了变化。压力-温度-时间结果表明，造山岩心在37 Ma处的厚度为17 km。假设沿从81°E到85°E的走向保持恒定，则表明尼泊尔西部和中部喜马拉雅山分别增厚了0.5倍和1-1.5倍。古尔拉·曼达塔（Gurla Mandhata）以西的造山岩心明显更薄，位于一个面积达11,000平方公里的新近纪盆地（Zhada）之下。在尼泊尔西部的穆古-多尔帕地区，一个与推力双工相关的宽而厚的造山岩芯与一个8500 km2高海拔，低起伏的地表并置。我们建议，这些结果可以通过沿大推力的斜交会解释，并受沿大推力的前斜向和斜向倾斜影响的沿走向和下倾的非均质耦合模式的解释。压力-温度-时间结果表明，造山岩心在37 Ma处的厚度为17 km。假设沿从81°E到85°E的走向保持恒定，则表明尼泊尔西部和中部喜马拉雅山分别增厚了0.5倍和1-1.5倍。古尔拉·曼达塔（Gurla Mandhata）以西的造山岩心明显更薄，位于一个面积达11,000平方公里的新近纪盆地（Zhada）之下。在尼泊尔西部的穆古-多尔帕地区，一个与推力双工相关的宽而厚的造山岩芯与一个8500 km2高海拔，低起伏的地表并置。我们建议，这些结果可以通过沿大推力的斜交会解释，并受沿大推力的前斜向和斜向倾斜影响的沿走向和下倾的非均质耦合模式的解释。压力-温度-时间结果表明，造山岩心在37 Ma处的厚度为17 km。假设沿从81°E到85°E的走向保持恒定，则表明尼泊尔西部和中部喜马拉雅山分别增厚了0.5倍和1-1.5倍。古尔拉·曼达塔（Gurla Mandhata）以西的造山岩心明显更薄，位于一个面积达11,000平方公里的新近纪盆地（Zhada）之下。在尼泊尔西部的穆古-多尔帕地区，一个与推力双工相关的宽而厚的造山岩芯与一个8500 km2高海拔，低起伏的地表并置。我们建议，这些结果可以通过沿大推力的斜交会解释，并受沿大推力的前斜向和斜向倾斜影响的沿走向和下倾的非均质耦合模式的解释。