Experimental constraints on the rheology of the mantle lithosphere at the base of the seismogenic zone

地震带底部地幔岩石圈流变学的实验约束

基本信息

批准号：
2054522
负责人：
James Hirth
金额：
$ 42.22万
依托单位：
Brown University
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2021
资助国家：
美国
起止时间：
2021-05-15 至 2025-04-30
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2054522&HistoricalAwards=false
关键词：
Experimental constraints rheology mantle lithosphere

项目摘要

The largest and most damaging earthquakes occur along plate boundaries where lithosphere is subducted beneath the continents. Geoscientists have discovered that a wide range of fault slip processes occur in these regions, and significant progress has been made understanding these events by integrating geophysical observations with models and constraints from lab experiments. However, there are still gaps in our understanding of mechanical properties at the relevant conditions. Previous work at these conditions has been hindered by relatively poor resolution of the stresses being imposed on the sample during an experiment. The investigators have made new modifications to their high-pressure equipment that will lead to significant improvement in the ability to measure stress and characterize the fault slip behavior that occurs within the subduction zone environment. The results will provide new constraints necessary to understand how earthquake slip initiates and to explain why there is a limited depth range over which the earthquakes occur. The project will fund two Ph.D. students (one completing a thesis and another starting a thesis during the duration of the project). Outreach will be coordinated with the Department’s DEEPS STEP (STEM in Providence Public Schools) program. Engagement in rock mechanics, with its strong links to engineering, has the potential to bridge a gap to URM STEM students, who remain dramatically underrepresented in Earth Sciences.This project involves experiments to: (a) quantify frictional behavior at high-temperature under both dry and wet conditions; (b) investigate low temperature plasticity of olivine aggregates at high pressure conditions near the brittle-plastic transition, which is also relevant for constraining the extrapolation of rate-and-state friction laws to mantle conditions; (c) constrain the role of dehydration reactions on the frictional stability of the lithosphere; and (d) determine frictional behavior and flow law parameters for alteration phases at high pressure to constrain the strength of altered lithosphere (and stress state prior to dehydration). The improvements to the investigator's apparatus enhances the ability to: (a) conduct creep tests, which will allow acquisition of better data to constrain flow law parameters; and (b) resolve transient deformation, which significantly improves the ability to quantify rate-and-state friction parameters at the high pressure conditions where seismicity occurs. The results will provide constraints for a wide range of scientists interested in the diverse fields of metamorphism, geodynamics, seismology, the physics of earthquakes, and fluid transport.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.

最大，最具破坏性的地震发生在岩石圈延伸下方的板块边界上。地球科学家发现，在这些地区发生了广泛的断层滑移过程，并且通过将地球物理观测与模型和实验实验的约束相结合，从而使这些事件取得了重大进展。但是，在相关条件下，我们对机械性能的理解仍然存在差距。在这些条件下，以前的工作受到了实验期间在样品上施加的应力的相对分辨率的相对较差的阻碍。研究人员对其高压设备进行了新的修改，这将导致测量压力的能力显着提高并表征俯冲带环境中发生的断层行为。结果将提供必要的新约束，以了解地震滑动如何启动，并解释为什么发生地震的深度范围有限。该项目将资助两家博士学位。学生（一个在项目期间完成论文，另一个完成论文）。外展将与该部门的深度步骤（Providence公立学校的STEM）协调。参与岩石力学，与工程有很强的联系，有可能在地球科学中弥合乌尔姆茎学生的差距，他们在地球科学中的人数仍然很少。（b）研究在脆性塑料过渡附近的高压条件下橄榄石聚集体的低温可塑性，这也与将速率和状态摩擦定律的外推到地幔条件相关；（c）限制脱水反应对岩石圈摩擦稳定性的作用；（d）确定在高压下改变阶段的摩擦行为和流量法参数，以限制岩石圈改变的强度（以及脱水之前的应力状态）。研究者设备的改进增强了：（a）进行蠕变测试的能力，这将允许获取更好的数据以限制流量法参数；（b）解决瞬态变形，这显着提高了在发生地震性的高压条件下量化速率和摩擦参数的能力。结果将为对变质，地球动力学，地震学，地震学，地震物理学和流体运输的潜水员领域感兴趣的广泛科学家提供限制。该奖项反映了NSF的坚定使命，并被认为是通过基金会的知识绩效和更广泛影响的评估来审查审查标准，通过评估通过评估来获得支持。