Collaborative Research: Active deformation and exhumation at the transition from subduction to oblique collision in Central New Zealand

地球的外壳由刚性构造板块组成，这些板块主要沿着它们的边缘相互作用。有几个因素控制着这些相互作用，包括板块的组成（海洋板块与大陆板块）和板块之间的相对运动感（碰撞、分离或相互滑动）。这些因素共同控制着沿构造板块边界表现出来的自然灾害，包括地震、滑坡、海啸和火山爆发。由于地球的构造板块不是静态的，构造板块边界的分布和特征随着地质年代的变化而变化。因此，要理解板块边界的危险，就需要对它们随着板块运动和特征的变化而发生的演变有一个全面的认识。2016年新西兰奥特罗阿发生的里氏7.8级Kaikōura地震发生在一个关键的板块构造过渡带，在这里，板块边界从俯冲（大洋板块被大陆板块吞噬）转变为走滑（彼此平行滑动），最终发生大陆碰撞。这次事件的变形程度和引发的滑坡突出了与主要板块边界过渡相关的复杂危害。这项研究将通过研究2016年地震周围地区的活动断层和隆起基岩的冷却年龄，揭示板块过渡是如何演变的。这项研究的影响包括推进科学知识和培养研究生，从而为具有全球竞争力的科学劳动力做出贡献。该项目通过让美国学生参与合作的国际实地工作，加强了国内和国际伙伴关系，并加深了美国和新西兰研究人员之间的联系。研究人员将开发一个国际大学系列研讨会，重点是探索将土著知识和地球科学研究结合起来的双文化方法。在坎特伯雷大学的新西兰合作者和Māori顾问的帮助下，调查人员将利用他们与土著和少数民族社区的机构联系，扩大这些群体对研讨会和地质实地研究的参与。最后，该项目将通过支持西华盛顿大学和密歇根大学新的和现有的分析能力来加强研究和教育基础设施。本项目通过收集和整合新西兰北坎特伯雷地区的新构造和低温热年代学资料，重点研究从俯冲到斜碰撞的板块边界过渡的地壳变形演化。具体的研究任务包括：(1)表征2016年Kaikōura地震震源周围未被充分研究的构造的浅层断裂速率和运动学特征；(2)测量该地区主要河流沿断层相关褶皱的切割河流面差异隆升；(3)量化与俯冲向斜碰撞过渡相关的基岩挖掘的开始、速率和空间模式。这些任务针对与板块边界迁移力学和运动学相关的现有知识空白，并将阐明突出的研究问题，包括：板块边界终端如何随时间迁移，以及新的板块边界结构发展的断层生长机制是什么？是否有可测量的“弓形波”或“尾流”参与这种影响地壳变形和挖掘的迁移？在多个地震旋回中，俯冲板块在控制俯冲终点的变形方面起什么作用？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。

Earth’s outer shell consists of rigid tectonic plates that interact primarily along their edges. Several factors control these interactions, including the composition of the plates (oceanic versus continental) and the relative sense of motion between them (colliding, diverging, or sliding past one another). These factors combined control the natural hazards expressed along tectonic plate boundaries, including earthquakes, landslides, tsunamis, and volcanoes. Because Earth’s tectonic plates are not static, the distribution and character of tectonic plate boundaries change over geologic time. As such, understanding plate-boundary hazards requires a comprehensive view of their evolution in response to changes in plate motions and character. The 2016 M7.8 Kaikōura earthquake in Aotearoa New Zealand occurred at a critical plate tectonic transition zone, where the boundary changes from subduction (oceanic plate consumed beneath continental) to strike slip (sliding parallel to one another) and ultimately continental collision. The extent of deformation and triggered landslides in this event highlight the complex hazards associated with a major plate-boundary transition. This study will shed light on how plate transitions evolve by studying active faults and cooling ages of uplifted bedrock in the area surrounding the 2016 earthquake. Impacts of this study include advancing scientific knowledge and training graduate students, thereby contributing to a globally competitive scientific workforce. The project bolsters domestic and international partnerships by engaging US students in collaborative, international field work, and deepens connections between US and New Zealand researchers. The investigators will develop an international university seminar series focused on exploring bicultural approaches to weaving indigenous knowledge and geoscience research. With New Zealand collaborators and Māori advisors at the University of Canterbury, the investigators will build on their institutional connections to indigenous and minoritized communities to broaden participation of these groups both in the seminar and in geological field research. Finally, this project will enhance research and educational infrastructure by supporting new and existing analytical capacities at Western Washington University and the University of Michigan.This project focuses on the evolution of crustal deformation across a plate-boundary transition from subduction to oblique collision through collection and integration of new neotectonic and low-temperature thermochronologic data in North Canterbury, New Zealand. Specific research tasks include: (1) characterizing the rate and kinematics of shallow faulting for understudied structures surrounding the epicentral region of the 2016 Kaikōura earthquake, (2) measuring differential uplift from incised fluvial surfaces along major rivers transecting fault-related folds in this area, and (3) quantifying the onset, rate, and spatial pattern of bedrock exhumation associated with the transition from subduction to oblique collision. These tasks target existing knowledge gaps related to the mechanics and kinematics of plate boundary migration, and will shed light on outstanding research questions including: How do plate-boundary terminations migrate over time, and what are the fault growth mechanisms through which a new plate-boundary structure develops? Is there a measurable “bow wave” or “wake” attending this migration that impacts crustal deformation and exhumation? What is the role of the subducting slab in controlling deformation at a subduction termination over multiple earthquake cycles?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.