Along-strike variations in active faulting in the northwest Himalaya with implications for the evolution of the Himalaya

点击翻译按钮获取中文摘要

This research program will define the 3-D geometry of active faults across a portion of the northwestern Himalayan mountain range and evaluate how these faults have moved through time. It is these faults that accommodate the convergence associated with the collision of the Indian and Eurasian tectonic plates. The focus will be on a ~500 km long region astride the trans-Himalayan drainage divide between the Indus and Ganges river systems, where preliminary data indicate that there could be marked range-parallel changes in fault structure and associated landscape evolution. The research program will test for a regional westward decrease in total shortening, a measurement of the total amount of mountain building that has occurred due to the collision of the Indian and Eurasian tectonic plates. Historically, the active faults in the Himalaya have been difficult to identify because many of the faults that are seismically active are not exposed at the Earth’s surface and are also difficult to image. To overcome these challenges, this study will use a combination of proxies that together will identify the active faults and how they have evolved through time. These methods include: 1) analysis of the shape of river systems and how they are affected by faulting; 2) measurement of rates of erosion and unroofing across the landscape; and 3) cross section balancing that will provide estimates of total shortening. The research program will link these rates of erosion and shortening amounts to rock uplift caused by the active faulting, whether the faults intersect the Earth’s surface or not. This research program will provide significant advances in our understanding of how the entire Himalayan system has evolved, with relevance to seismology, geomorphology, tectonics and humankind in the region. The implications for the seismic cycle are particularly relevant given the region’s recognized seismic risk and dense population (> 10 million people). For instance, because earthquake magnitude is related to fault size, the geometry of active fault systems is important information in assessing where the largest earthquakes are likely to occur, and on which fault planes. Given the prediction that this region is overdue for large (and likely devastating) earthquakes, the region’s seismic potential has relevance to the many that inhabit the region and to India’s geopolitical partners, including Canada. An important aspect of the program will be to train Canadian students in the cutting-edge techniques that link geomorphology to active tectonics. Students will have the opportunity to gain such skills based on digital, laboratory and field datasets that they will be involved in collecting. The approach can be applied to understand the distribution of active deformation and seismic hazards in any actively deforming region on Earth, including the Cascadia subduction zone along the west coast of Canada.