Collaborative Research: A Geochemical Approach to Quantifying the Magnitude of Strain and Fluid Flow along the Subduction Interface

合作研究：量化沿俯冲界面的应变和流体流动大小的地球化学方法

• 批准号: 2214324
• 负责人: Donald Fisher
• 金额: $ 51.86万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-07-15 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2214324&HistoricalAwards=false
• 关键词: Collaborative; Research; Geochemical; Approach; Quantifying

Earth’s largest earthquakes occur along the megathrusts (the subduction plate interfaces) that separate rigid tectonic plates in subduction zones. The accumulation and release of elastic strain along these plate interfaces is predicated on the “healing” of the interface after the large earthquakes. This project will characterize the chemical and mechanical processes that control this healing during the time between earthquakes. Observations of ancient subduction interfaces, now exposed on land, will be used to inform a numerical model for slip and fluid flow. Together, these approaches will allow the investigators to determine how subduction zone processes impact the spatial and temporal patterns of earthquakes—an important step in assessing the hazards associated with active subduction zones. The study includes support for an early-career faculty member, a Ph.D. student, and nine undergraduates. Six of the undergraduates will be recruited from University of the Incarnate Word, an undergraduate body that serves a local Hispanic community.This project comprises a structural and geochemical investigation of two exhumed terrains that preserve a record of the physical and chemical conditions relevant to the plate interface of the global array of active subduction zones. Combined, the Shimanto belt in Japan and the Kodiak Accretionary complex in Alaska, form a composite record spanning depths from 8 to 20 km and peak temperatures between 150 and 350˚C. Electron-microscope-based elemental mapping of samples collected during several field campaigns will enable quantification of mineral phases and their redistribution with progressive strain. Combined cathodoluminescence mapping, electron backscatter diffraction, and fluid-inclusion microthermometry will constrain paleotemperatures and finite strain, and identify deformation mechanisms. Quantitative estimates of strain rate will be derived by combining strain magnitudes with field observations of shear zone thickness and present-day estimates of plate convergence rate. These measurements and observations will be used to inform a numerical model that parameterizes the effects of seismic slip, fluid flow and interseismic restrengthening on the temporal and spatial distribution of earthquakes on the plate interface. The multidisciplinary workplan is designed to address the following fundamental questions: Q1) What are the magnitudes of volume strain and shear strain associated with interseismic deformation? Q2) Is there a balance between dissolution along the scaly fabric and precipitation of minerals within cracks in blocks? Q3) What are the relative contributions to quartz vein formation of local diffusive mass transfer of silica versus the influx of dissolved silica by an externally derived fluid? Q4) How does partitioning of deformation mechanisms vary from the updip to the downdip ends of the seismogenic zone?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.

地球上最大的地震发生在巨型（俯冲板界面）沿俯冲带中的刚性构造板分开。大地震后，界面的“愈合”预测了沿这些板界面的弹性应变的积累和释放。该项目将表征在地震之间控制这种愈合的化学和机械过程。现在暴露在陆地上的古代俯冲界面的观察将用于告知滑动和流体流量的数值模型。这些方法将共同确定俯冲带过程如何影响地震的空间和临时模式，这是评估与主动俯冲带相关的危害的重要步骤。该研究包括对早期职业教师博士学位的支持。学生和九个本科生。六名大学生将从化身词的大学招募，这是一个为当地的西班牙裔社区服务的本科生。该项目包括两个被灌输的地形的结构性和地球化学投资，可保留与活跃的超身Zone的全球板界面界面界面相关的物理和化学条件的记录。结合在一起，日本的光环带和阿拉斯加的Kodiak增生综合体形成了从8到20 km的复合记录，峰值温度在150至350°C之间。基于电子 - 微观的元素映射在几个现场活动期间收集的样品，将实现矿物相及其逐渐菌株的重新分布。共有的阴极发光映射，电子反向散射衍射和流体包含微热计量法将限制古植物和有限应变，并确定变形机制。应变率的定量估计将通过将应变幅度与剪切区厚度的现场观测和板收敛速率的当前估计值结合来得出。这些测量和观察结果将用于告知一个数值模型，该模型参数化地震滑动，流体流量和经过震撼的恢复对板界面上地震的临时和空间分布的影响。多学科工作场所旨在解决以下基本问题：Q1）与跨界变形相关的体积应变和剪切应变的幅度是什么？ Q2）沿着鳞状织物的溶解与块裂缝内的矿物沉淀之间存在平衡吗？ Q3）二氧化硅的局部不同传质的相对贡献与外部衍生的流体的溶解二氧化硅的影响是什么？ Q4）变形机制的分区如何从更新到地震生成区的下dip末端的不同？该奖项反映了NSF的法定任务，并通过使用基金会的知识分子优点和更广泛的影响审查标准来通过评估来诚实地获得支持。