An Experimental Study on the Role of Pore Fluid Pressure During Slow Slip in Subduction Zones

梅洛迪·弗兰奇博士获得了美国国家科学基金会地球科学博士后奖学金，将在马里兰大学帕克学院开展一项研究和教育计划。她将使用实验方法来描述孔隙流体压力对俯冲带岩石滑动过程的影响。地球物理观测表明，高流体压力出现在以慢滑为特征的俯冲带区域，这是介于标准地震活动和稳定蠕变之间的行为。尽管慢滑动可能会增加孕震板块边界的剪应力，并可能导致破坏性地震的孕育，但在相应的压力和温度条件下，极高的流体压力对滑动过程的影响知之甚少。这项研究计划的结果将限制导致俯冲带缓慢滑动的过程。本科生将被包括在研究的执行中，作为他们高级论文要求的一部分。除了在研究的技术方面与学生合作外，弗兰奇博士还将指导学生满足发展他们的科学交流技能的要求。与缓慢滑动相关的地震危险包括(1)沿俯冲带上倾孕震部分触发地震活动，(2)地震滑动事件向下倾斜和向陆地传播。这项工作的重点是确定慢滑的微观机制，并提供可用于模拟与慢滑事件相关的地震危险性的本构关系。为了实现这些目标，弗兰奇博士将进行一系列实验研究，以记录在发生缓慢滑动的温度和应力条件下的断层和滑动。在富含反蛇纹岩的蛇纹岩中，将确定高孔隙流体压力和增加孔隙流体压力对失效率、应力降和强度的影响。一组新的实验应力路径将被用来检验已发表的和关于孔隙流体稳定效应的新假说。除了实验工作外，详细的微观结构分析将表征和量化导致慢滑行为的变形机制。

Dr. Melodie French has been granted an NSF Earth Sciences postdoctoral fellowship to carry out a research and education plan at the University of Maryland, College Park. She will use experimental methods to characterize the effects of pore fluid pressure on slip processes in subduction zone rocks. Geophysical observations indicate that high fluid pressures occur in regions of subduction zones characterized by slow slip, which is behavior intermediate between standard seismicity and steady creep. Despite the fact that slow slip likely increases shear stress on the seismogenic plate boundary and may contribute to the nucleation of destructive earthquakes, little is known about the effects of very high fluid pressure on slip processes at the relevant pressure and temperature conditions. The results of this research program will constrain the processes that cause slow slip in subduction zones. Undergraduate students will be included in the execution of the research as part of their senior thesis requirements. In addition to working with students on the technical aspects of the research, Dr. French will mentor students in fulfilling requirements that develop their scientific communication skills.Seismic hazards associated with slow slip include (1) triggered seismicity along the updip seismogenic portion of subduction zones and (2) downdip and landward propagation of a seismic slip event. The focus of this work is to determine the micro-mechanisms of slow slip, and to provide constitutive relations that can be used to model seismic hazards associated with slow slip events. To accomplish these goals, Dr. French will conduct a set of experimental studies to document faulting and slip under the temperature and stress conditions that slow slip occurs. The effects of both high and increasing pore fluid pressure on failure rates, stress drops, and strength will be determined in antigorite-rich serpentinite. A set of novel experimental stress paths will be employed to test published and new hypotheses on the stabilizing effects of pore fluid. In addition to the experimental work, detailed microstructural analyses will characterize and quantify the deformation mechanisms that cause slow slip behavior.