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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.

最大和最具破坏性的地震发生在沿着板块边界，岩石圈俯冲到大陆之下。地球科学家发现，在这些地区发生了广泛的断层滑动过程，通过将地球物理观测与实验室实验的模型和约束相结合，在理解这些事件方面取得了重大进展。然而，我们对相关条件下的力学性能的理解仍存在差距。由于实验期间施加在样品上的应力分辨率相对较差，之前在这些条件下的工作受到了阻碍。研究人员对他们的高压设备进行了新的修改，这将大大提高测量应力和描述俯冲带环境中发生的断层滑动行为的能力。研究结果将提供新的必要的限制，以了解地震滑动如何启动，并解释为什么有一个有限的深度范围内发生的地震。该项目将资助两名博士。学生（一个完成论文，另一个在项目期间开始论文）。外联活动将与教育部的DEEPS STEP（普罗维登斯公立学校的STEM）计划协调。参与岩石力学，与工程密切相关，有可能弥补URM STEM学生的差距，他们在地球科学方面的代表性仍然显着不足。该项目涉及实验：（a）量化干燥和潮湿条件下高温下的摩擦行为;（B）研究橄榄石聚集体在接近脆塑性转变的高压条件下的低温塑性，这也是相关的约束速率和状态摩擦定律的地幔条件外推：（c）约束脱水反应的岩石圈摩擦稳定性的作用;确定高压下蚀变相的摩擦行为和流动规律参数，以约束蚀变岩石圈的强度（以及脱水前的应激状态）。对调查人员的仪器进行改进，提高了以下能力：（a）进行蠕变试验，这将能够获得更好的数据，以限制流动定律参数;（B）解决瞬态变形，这大大提高了在发生地震的高压条件下量化速率和状态摩擦参数的能力。研究结果将为对变质作用、地球动力学、地震学、地震物理学和流体输运等不同领域感兴趣的科学家提供约束。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。