Low-Frequency Attenuation in Polycrystalline Silicates and Silicate Partial Melts

多晶硅酸盐和硅酸盐部分熔体的低频衰减

• 批准号: 0106620
• 负责人: Reid Cooper
• 金额: $ 8.7万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-08-01 至 2003-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0106620&HistoricalAwards=false
• 关键词: Low; Frequency; Attenuation; Polycrystalline; Silicates

Cooper 0106620 The experimental measurement of the low-frequency attenuation behavior of polycrystalline olivine, of olivine-orthopyroxene and of olivine-based partial melts is the practical emphasis of this research. Of theoretical focus is a new hypothesis concerning the physical mechanism(s) and significance of the "high-temperature background" mechanical absorption, specifically, that this absorption relates to the diffusion-effected relaxations of grain and solid-state phase boundaries and particularly of (deformation-induced) subgrain boundaries. The physical implication, then, is that a small-amplitude, oscillatory variation in stress, one that is added to a nominally constant differential stress that is effecting dislocation creep in a material, is "sampling" the deformation-induced microstructure, specifically the network of subgrains. If this hypothesis is correct--and discerning this correctness is the long-range goal of the experimental work--one can envision an effective way to do attenuation-based "geophysical prospecting" of active tectonic regions, e.g., for levels of differential stress and, perhaps, strain, with a calibration based on laboratory experiments. Experiments in this (one-year) funding period will emphasize dynamic ("sub-resonant" oscillatory loading) and quasi-static (constant loading, i.e., creep), high-resolution torsional mechanical responses of carefully engineered aggregates of (ferromagnesian) olivine and of two-phase solid olivine-orthopyroxene. These will be studied as functions of (i) temperature (1150-1350 degC), (ii) frequency (10^[-4]-1 Hz) and (iii) grain size (5-20 micrometers; fine enough that [a] thermal-expansion-anisotropy effected grain/phase boundary cracking cannot occur and [b] [for the levels of differential stress employed] lattice dislocations are not nucleated in the course of mechanical testing). In addition, benchmarking deformation experiments, comparing the high-resolution ambient-pressure measurements with the mechanical response of the same material under a confining pressure of ~300 MPa will be performed.

Cooper 0106620多晶橄榄石，橄榄石 - 异拷二烯和基于橄榄石的部分熔体的低频衰减行为的实验测量是这项研究的实际强调。 理论重点是一种关于物理机制的新假设和“高温背景”机械吸收的意义，特别是，这种吸收与晶粒和固态相边界的扩散弛豫有关，尤其是（变形诱导的）亚晶界的扩散弛豫。 因此，物理上的意义是，应力的振幅较小，振荡变化，这种变化被添加到材料中脱位的名义恒定的差分应力中，是“对”变形诱导的微结构，特别是亚级网络。 如果该假设是正确的 - 并且辨别实验工作的远距离目标 - 一个人可以设想一种有效的方法来对主动构造区域进行基于衰减的“地球物理勘探”，例如，对于基于实验室实验的校准，例如，对于差异压力的水平，也许是应变的水平。 在此（一年）资金期间的实验将强调动态（“谐波”振荡载荷）和准静态（持续的载荷，即蠕变），高分辨率的扭转机械响应（Ferromagnesian）橄榄石的精心设计的核心量，并具有两相固体固体固体olivine-Olivine-Ortopy-Ortopropy。这些将作为（i）温度（1150-1350摄氏度），（ii）频率（10^[-4] -1 Hz）和（iii）晶粒尺寸（5-20​​微米；足够细细布晶粒 - 异位疗法的晶粒/相位边界裂纹产生的晶粒裂纹的晶粒裂纹和[b] [b] [b] [b] [b] [b] [b] [b] [b] [b] [b] [b] [b] [b] [b] [b] [测试）。 此外，将进行基准变形实验，将高分辨率的环境压力测量与在约300 MPa的近约压力下的机械响应进行比较。