Investigation of High Pressure Faulting Associated with the Olivine-Spinel Transition and Evaluation of the Anticrack Theory of Deep-Focus Earthquakes

与橄榄石-尖晶石转变相关的高压断层研究及深源地震反裂纹理论评价

• 批准号: 8915938
• 负责人: Harry Green
• 金额: $ 13.94万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1990
• 资助国家: 美国
• 起止时间: 1990-02-15 至 1993-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8915938&HistoricalAwards=false
• 关键词: Investigation; Pressure; Faulting; Associated; Olivine

The underlying failure mechanism responsible for deep-focus earthquakes has remained unknown since their discovery almost 70 years ago. High pressure faulting was discovered in specimens of Mg2GeO4 olivine deformed in the spinel stability field under conditions where the kinetics of the transformation become just possible on the time-scale of the experiment. Very fine-grained spinel is found in the fault zones. The PIs pose four major questions: (i) Are microanticracks unstable? (ii) What is the process by which mode -I anticrack link-up leading to through- going faults? (iii) Which transformation mechanism operates at the tips of anticracks? (iv) Does the anticrack mechanism operate in the x - B transformation? They will answer question (i) by instrumenting the high pressure apparatus and determining quantitatively the abundance, magnitude, time-dependence and wave form of acoustic emissions before and during failure. Questions (ii) and (iii) will be pursued by electron channeling scanning electron microscopy and transmission electron microscopy to determine the size, shape, orientation and spatial distribution of microanticracks and the grain-size and crystallographic orientation of spinel crystals within them with respect to the host olivine crystals. Question (iv) will be investigated by conducting deformation experiments on Mn2Geo4 olivine within the B stability field in HWG's unique 5GPa deformation apparatus.

深震源地震的潜在破坏机制自近70年前发现以来一直不为人知。在实验时间尺度上，当Mg2GeO4橄榄石在尖晶石稳定场中变形时，发现了高压断裂。在断裂带中发现了细粒尖晶石。pi提出了四个主要问题：(i)微裂纹不稳定吗？（ii） i型裂纹连接导致贯穿性故障的过程是什么？（iii）哪一种转变机制在防锈药的尖端起作用？（iv）裂纹机制是否在x - B转换中起作用？他们将回答问题(i)，通过测量高压仪器，定量地确定故障前和故障期间声发射的丰度、大小、时间依赖性和波形。问题（ii）和（iii）将通过电子通道扫描电子显微镜和透射电子显微镜进行研究，以确定微裂纹的大小、形状、取向和空间分布，以及其中尖晶石晶体相对于寄主橄榄石晶体的晶粒尺寸和晶体取向。问题（iv）将通过在HWG独特的5GPa变形装置中对Mn2Geo4橄榄石进行B稳定场的变形实验来研究。