In Situ Estimation of Poisson's Ratio

泊松比的原位估计

• 批准号: 0838346
• 负责人: Guoqing Lin
• 金额: $ 8.71万
• 依托单位: University of Miami
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-15 至 2011-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0838346&HistoricalAwards=false
• 关键词: Situ; Estimation; Poisson; Ratio

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Seismologically determined Poisson's ratio is a powerful tool to complement the petrological and geochemical studies in the investigation of the composition of the Earth. In this project, the researchers will estimate the ratio of compressional- to shear-wave velocity (Vp/Vs), which is directly related to Poisson's ratio, using the technique of Lin and Shearer (2007). This approach applies a robust least-squares method to arrival time differences for P and S waves obtained from waveform cross-correlation. It provides highly precise results because cross-correlation can measure differential times to within a few milliseconds and can achieve a precision of 0.001 in estimated Vp/Vs ratio, corresponding to about 0.0004 in Poisson's ratio. The proposed work includes performing waveform cross-correlation and applying the in-situ method to several regions. The focus areas of application are volcanoes and active fault zones, including Yellowstone, Mount Etna Volcano in Italy, Long Valley Caldera, the Loma Prieta rupture zone, and the SAFOD target event region for Parkfield. The spatial and temporal variations in the resulting Vp/Vs ratios will help to track movement of magma and volatiles within a volcano and to estimate spatial variations in fracturing and fluid content in active fault zones. The high-precision Vp/Vs ratio in the source region will also be used to improve earthquake location accuracy.The method the researchers will apply is simple to implement and fast to execute since it uses a robust least-squares to fit the differential times. Another advantage of this method is that it will be straightforward to study the spatial and temporal variations of Vp/Vs ratios by simply selecting a subset of events by space and/or time, which would be difficult to achieve based on tomography because of the difficulties of obtaining reliable Vp/Vs models and the non-uniqueness of the problem. The Vp/Vs ratios can be obtained even without S-wave catalog picks, because only the differential times are needed and the time window for S cross-correlation can be estimated from the earthquake locations and a given velocity model.

该奖项是根据2009年的《美国复苏和再投资法》（公法111-5）资助的。从而确定的泊松比是对地球组成的研究，是补充岩石学和地球化学研究的强大工具。在这个项目中，研究人员将使用Lin和Shearer（2007）的技术估算与泊松比直接相关的压缩波与剪切波速度（VP/VS）的比率。这种方法将坚固的最小二乘方法应用于从波形互相关获得的P和S波的到达时间差。它提供了高度精确的结果，因为互相关可以在几毫秒内测量差分时间，并且可以在估计的VP/VS比率中获得0.001的精度，相当于泊松比的0.0004。拟议的工作包括执行波形互相关并将原位方法应用于多个区域。应用的焦点区域是火山和活动断层区，包括黄石，意大利的埃特纳火山，朗谷火山口，洛马普利埃（Loma Prieta）破裂区和帕克菲尔德（Parkfield）的Safod目标事件区域。由此产生的VP/VS比率的空间和时间变化将有助于跟踪火山中岩浆和挥发物的运动，并估计活动断层区域中分裂和流体含量的空间变化。 源区域中的高精度副总裁/VP比率也将用于提高地震位置的精度。研究人员将应用的方法易于实现，并且可以快速执行，因为它使用了坚固的最小二乘来适合差异时期。该方法的另一个优点是，通过简单地选择按空间和/或时间选择事件的子集，研究VP/VS比率的空间和时间变化将是很简单的，因为获得可靠的VP/VS模型以及问题的非唯一性，这将很难基于层析成像实现。即使没有S-Wave目录选拔，也可以获得VP/VS比率，因为只需要差分时间，并且可以从地震位置和给定的速度模型中估算S交叉相关的时间窗口。