Collaborative Research: How does it end? Exploring thrust terminations of an intra-continental strike-slip fault, north Tibet

板块构造理论认为，内部刚性构造板块沿着狭窄的板块边界相互作用。然而，变形通常分布在大陆的内部，例如在喜马拉雅山脉带东北部的亚洲大陆，在距离印度板块和欧亚板块边界一千多公里的地方发生了重大的断裂和褶皱。该地区一些最大的特征是东西向的走滑断裂，如藏北的海原断裂。本项目以海原断裂西端为研究对象，探讨了山带内部从走滑断层运动到褶皱逆冲断层的变形变化规律。此外，像海原断层这样的构造是亚洲大陆人口稠密地区的主要地震危险源。因此，限制沿这些走滑断层长度的变形形式、幅度和速率将有助于未来的灾害和风险评估。该项目的其他社会相关影响包括：支持早期职业教师建立具有全球竞争力的研究项目；培养一名科学、技术、工程和数学（STEM）学科的博士生和两名本科生；与研究人员和机构的国际合作；开展社区参与活动，重点关注地震灾害。该项目还支持开发一个对公众开放的现代地质测绘网站，该网站以数字平板实地测绘和数字高程模型（DEM）构建的技术和信息为特色，包括将地图数据纳入开放获取的在线档案的方法。大陆内部对边缘驱动的板块边界条件的响应是大陆构造学的中心问题。喜马拉雅—青藏造山带是新生代印度—亚洲渐进汇聚的产物，造山带内部最大的构造是大型走滑断裂。因此，西藏是一个理想的试验场，可以确定走滑断层如何在碰撞造山带中容纳和重新分配应变。多学科研究探讨了藏北海原左滑断裂西端走滑断裂向逆冲断裂的突变。具体而言，采用地质基岩和新构造填图相结合，利用构造-运动（SfM）方法构建数字高程模型（dem），地表年龄测年（即光激发发光和放射性碳）和低温热年代学来(1)约束海原西部断裂段第四纪滑动速率，(2)系统地记录走滑变形如何转移到范围边界。祁连山冲断带中部逆冲断裂体系。利用海原断裂西端运动的野外观测资料，对喜藏造山带板块辐合-正走滑断裂模型进行了验证，包括：(1)顺时针断层旋转模型、(2)挤压断层模型和(3)应变传递模型。对海原断裂的研究成果可以应用于其他陆内变形带。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Plate tectonic theory suggests that internally rigid tectonic plates interact with one another along narrow plate boundaries. However, deformation is often distributed across the interior of continents, such as in the Asian continent northeast of the Himalayan mountain belt, where significant faulting and folding occurs more than a thousand kilometers from the boundary between the Indian and Eurasian plates. Some of the largest features in the region are east-west oriented strike-slip faults, such as the Haiyuan fault in north Tibet. This project investigates the western termination of the Haiyuan fault to determine how deformation changes from strike-slip fault motion to folding and thrust faulting within the interior of the mountain belt. Furthermore, structures like the Haiyuan fault are sources of major seismic hazards for densely-populated regions within the Asian continent. Thus, constraining the style, magnitude, and rate of deformation along the length of these strike-slip faults will aid in future hazard and risk assessment. Other societally relevant impacts of this project include: support of early-career faculty to establish globally competitive research programs; training a PhD student and mentoring two undergraduates in a science, technology, engineering and mathematics (STEM) discipline; international collaboration with researchers and institutions; and outreach at community engagement events with a focus on earthquake hazards. The project also supports the development of a modern publicly-accessible geologic mapping website that features techniques and information about digital tablet-based field mapping and digital elevation model (DEM) construction, including methods of incorporating map data into open-access online archives.The intra-continental response to edge-driven plate boundary conditions is a central topic in continental tectonics. The Himalayan-Tibetan orogen results from progressive Cenozoic India-Asia convergence, and the largest structures within the interior of this orogen are large strike-slip faults. Therefore, Tibet is an ideal testing ground to determine how strike-slip faulting accommodates and redistributes strain in a collisional orogen. This multidisciplinary investigation explores the western termination of the left-slip Haiyuan fault within northern Tibet, where strike-slip faulting abruptly transitions to thrust faulting. Specifically, a combination of geologic bedrock and neotectonics mapping, construction of digital elevation models (DEMs) using structure-from-motion (SfM) methods, surface-age dating (i.e., optically stimulated luminescence and radiocarbon), and low-temperature thermochronology are employed to (1) constrain Quaternary slip rates along the western Haiyuan fault segments, and (2) systematically document how strike-slip deformation transfers to a range-bounding, thrust-fault system in the central Qilian Shan thrust belt. Field observations of the kinematics of the western termination of the Haiyuan fault are used to test models for plate-convergence-normal strike-slip faulting in the Himalayan-Tibetan orogen, including (1) clockwise-fault rotation, (2) extrusion-fault models, and (3) strain transfer models. Insights gained from studying the Haiyuan fault can be applied to other zones of intra-continental deformation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.