How is topography maintained in the western Himalayan and where is plate convergence accommodated?

喜马拉雅山西部的地形是如何维持的？板块汇聚又在哪里？

• 批准号: 429470703
• 负责人: Privatdozent Dr. Rasmus C. Thiede
• 金额: --
• 依托单位: School of Earth and Space Exploration
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/429470703?language=en
• 关键词: How; topography; maintained; western; Himalayan

Despite major advances in understanding how plate motion is accommodated at convergent plate boundaries, it is still controversially debated how topography of orogenic fronts is sustained and where exactly plate convergence is partitioned. This is reflected by frequently contradictory short- and long-term derived crustal shortening rates and their interpretation in the context of the seismotectonic segmentation of range fronts - a problem that may be intimately associated with temporal and spatial variations of deformation in orogenic wedges. Are such disparate levels of activity systematic or are they triggered by random processes? Answering this question is fundamental for understanding the mechanisms and loci of wedge deformation and its timing, which is ultimately necessary for hazard mitigation and risk reduction in tectonically active mountain ranges. To address this problem obtaining deformation rates and measuring the locus of faulting on intermediate timescales is a key task to assess the deformation mechanisms and earthquake patterns and to decipher earthquake recurrence patterns.The Himalaya constitutes a stack of thrust sheets, i.e. the orogenic wedge, scraped off India as it is subducted beneath Tibet. All primary fault systems within the wedge sole into the Main Himalayan Thrust (MHT), the main basal décollement. Competing hypotheses suggest that Himalayan topography is sustained and plate convergence is accommodated by deformation either solely along the basal décollement or through more broadly distributed deformation across multiple thrust faults. However, both hypotheses could be true as orogenic wedge activity may be characterized by these end-member scenarios over time, depending on the criticality of the orogenic wedge, which is fundamentally influenced by accretion and erosion in the advancing thrusts.Based on my previous work in the region I hypothesize that the tectonics of the Himalayan wedge may indeed follow a pattern between two end-member deformation styles. The temporal and spatial variations in climate and erosion have generated ubiquitous Late Pleistocene and Holocene fluvial terraces across the entire length of the Himalayan front. The excellent preservation of these geomorphic features in the western Himalaya (73°E to 80°E), thus makes this region a prime area to quantify the timing of terrace formation and transient sediment loading, terrace abandonment and deformation. Here I propose to quantify potential links and interactions between crustal shorting, late Pleistocene sedimentary loading, Late Pleistocene and Holocene fault displacement rates, and erosion. Our ultimate goal is to quantify the spatial and temporal characteristics of mountain-front deformation in the context of orogenic wedge dynamics.

尽管在了解板块运动是如何在会聚的板块边界容纳的重大进展，它仍然是有争议的辩论如何维持地形的造山前和确切的板块会聚被分割。这是反映了经常矛盾的短期和长期推导的地壳缩短率和他们的解释范围内的地震构造分割的范围前-一个问题，可能是密切相关的时间和空间变化的变形造山楔。这种不同层次的活动是系统性的，还是由随机过程触发的？探讨这个问题对于理解楔状变形的机制和位置及其时间至关重要，这对于减轻构造活动山脉的灾害和减少风险至关重要。为了解决这一问题，获得中间时间尺度上的变形速率和测量断层的位置是评估变形机制和地震模式以及解释地震复发模式的关键任务。喜马拉雅山构成了一堆逆冲岩席，即造山楔，当它俯冲到西藏下面时，从印度刮下来。楔形体内的所有主要断层系统都进入主喜马拉雅逆冲断层（MHT），即主要的基底滑脱。相互竞争的假说表明，喜马拉雅地形是持续的，板块会聚是通过变形来适应的，要么是仅仅沿着基底滑脱，要么是通过更广泛地分布在多个逆冲断层上的变形。然而，这两种假设可能是真实的造山楔活动的特点可能是这些端员的情况下，随着时间的推移，取决于造山楔的临界性，这是从根本上影响的增生和侵蚀的推进thrusts.Based我以前的工作在该地区，我假设喜马拉雅楔的构造可能确实遵循两个端员之间的变形样式的模式。气候和侵蚀的时间和空间变化产生了无处不在的晚更新世和全新世河流阶地跨越整个喜马拉雅山脉的长度。喜马拉雅西部（东经73°至80°）的地貌特征保存完好，因此，这一地区是量化阶地形成和瞬时沉积物负荷、阶地废弃和变形时间的主要地区。在这里，我建议量化潜在的联系和相互作用之间的地壳缩短，晚更新世沉积负荷，晚更新世和全新世断层位移率，和侵蚀。我们的最终目标是量化的造山楔动力学背景下的山前变形的时空特征。