Abstract

The tectonic activity in the Himalayan region is reflected through major and minor lineaments associated with the major fault and thrust systems. In the present study, we used multi-sensor optical and microwave radar remote sensing images and topographic elevation data for extraction of lineaments. Image enhancement of remote sensing data and relief shading of topographic elevation data were performed for highlighting the lineaments. Eight structural domains were selected in and around the major thrusts and strike slip faults in north-western and central Himalayan regions. From the angular distribution of lineaments, the vector mean orientations of major and minor lineaments were determined for each of the structural domains. Considering areal coverage of individual litho-units, area-weighted internal friction angles were obtained for eight structural domains. Finally, based on the Mohr-Coulomb failure criteria, the directions of maximum principal stress (s₁) were estimated from the orientations of shear fractures. The study shows a good agreement between minor lineaments based maximum principal stress directions and GPS based plate motion vectors. But, we found a significant deviation between major and minor lineaments based principal stress directions and plate motion vectors for some of the structural domains those were affected by post-thrusting strike-slip fault tectonics. This is perhaps due to the fact that major lineaments give rise to the maximum principal stress direction of older collision and post-collision phases whereas minor lineaments represent essentially recent to sub-recent active tectonics phase. Further, subtle local deviations in the principal stress directions may be attributed to litho-tectonic heterogeneities.

中文翻译：

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喜马拉雅山最大主应力方向分析：基于遥感的方法

摘要

喜马拉雅地区的构造活动通过与主要断层和逆冲系统相关的主要和次要构造反映出来。在本研究中，我们使用多传感器光学和微波雷达遥感图像和地形高程数据提取线迹。进行了遥感数据的图像增强和地形高程数据的浮雕阴影处理，以突出线条。在喜马拉雅西北和中部地区的主要逆冲和走滑断层及其周围地区选择了八个构造域。从线条的角度分布，确定每个结构域的主要和次要线条的矢量平均方向。考虑到各个岩石单元的面积覆盖率，获得了八个结构域的面积加权内摩擦角。最后，根据Mohr-Coulomb破坏准则，最大主应力的方向（s₁）是根据剪切裂缝的方向估算的。研究表明，基于较小主线的最大主应力方向与基于GPS的板块运动矢量之间具有良好的一致性。但是，对于受推后走滑断层构造影响的某些结构域，我们发现基于主要和次要构造的主应力方向和板块运动矢量之间存在显着偏差。这可能是由于以下事实：主要的纹路会引起较旧的碰撞阶段和碰撞后阶段的最大主应力方向，而次要的纹路实质上表示最近到近现代的活动构造阶段。此外，主应力方向上的细微局部偏差可归因于岩石构造非均质性。