Effect of seamount subduction on fault geometry and rupture propagation

克里斯汀·雷加拉博士在加拿大蒙特利尔的麦吉尔大学期间获得了美国国家科学基金会地球科学博士后奖学金，以开展一项研究和教育计划。她将研究俯冲海山附近不同的断层几何形状和强度对巨型逆冲断裂的成核和传播的作用。这项工作对理解控制大型逆冲地震成核和最大震级的过程具有直接意义。俯冲带产生世界上最大的地震和海啸，地震规模的限制部分取决于两个板块之间断层边界的几何形状。下行板块上的海山等粗糙点和凸起会影响板块边界断层的锁定程度，并调节地震期间板块边界滑动的大小和分布。该项目的结果可应用于地震危险性评估，以帮助估计具有俯冲海山的巨型逆冲的最大破裂面积和力矩震级。该项目将为实地和基于模型的研究小组之间的知识共享创造机会，并将为Regalla作为一名早期职业科学家提供宝贵的专业发展。此外，该项目将包括本科生研究人员，从而为Regalla提供发展教育和指导技能的机会，并为本科生提供实践研究机会。尽管海山俯冲很常见，但关于海山是作为地震成核场所还是阻碍破裂传播的屏障，仍存在相当大的争议。这项工作将结合海山俯冲时活动的古板块边界逆冲断层的野外露头分析和动态破裂的有限元模型来评估所提出的地震破裂模型。该项目将首次对古海山已经俯冲到孕震深度的位置的俯冲推力的物理性质进行描述，并将在涉及俯冲海山的破裂的数值模拟中为断层几何形状和强度参数提供基于观测的模型约束。这项工作的结果将提供有关俯冲海山的结构容纳性及其对地震破裂传播的控制的信息。该研究金是与国际科学和工程综合活动办公室共同资助的

Dr. Christine Regalla has been awarded an NSF Earth Sciences Postdoctoral Fellowship to carry out a research and education plan while at McGill University in Montreal, Canada. She will investigate the role of variable fault geometry and strength in the vicinity of subducted seamounts on the nucleation and propagation of megathrust ruptures. This work has direct implications for understanding processes controlling the nucleation and maximum magnitude of large megathrust earthquakes. Subduction zones generate the world's largest earthquakes and tsunamis and the limits on earthquake size depend in part on the geometry of the fault boundary between the two plates. Rough spots and bumps such as seamounts on the down-going plate can affect the degree of locking along the plate boundary fault and modulate the magnitude and distribution of plate boundary slip during earthquakes. Results from this project can be applied to seismic hazard assessments to help estimate maximum rupture area and moment magnitude at megathrusts with subducted seamounts. This project will create opportunities for knowledge sharing between field and modeling-based research groups, and will provide valuable professional development for Regalla as an early-career scientist. In addition, this project will involve undergraduate student researchers, thereby providing opportunities for Regalla to develop educational and mentoring skills, and provide hands-on research opportunities for undergraduate students. Although the subduction of seamounts is common, there is considerable debate as to whether seamounts act as sites of earthquake nucleation or barriers that impede rupture propagation. This work will combine analyses of field outcrops of ancient plate boundary thrust faults that were active during seamount subduction with finite element models of dynamic rupture to evaluate proposed models of earthquake rupture. This project will provide the first known descriptions of the physical properties of the subduction thrust in locations where ancient seamounts have subducted to seismogenic depths, and will provide observationally-based model constraints for fault geometry and strength parameters in numeric simulations of rupture involving subducted seamounts. Results of this work will provide information on the structural accommodation of subducted seamounts and their control on earthquake rupture propagation.The fellowship is being co-funded with the Office of Integrated and International Activities - International Science and Engineering