Collaborative Research: Investigating the limits of ray-based global surface-wave tomography

该奖项是根据2009年美国复苏和再投资法案(公法111-5)资助的。该项目涉及对用于成像地球内部的不同技术方法的调查。关于地球深处的结构、组成和温度的许多已知信息来自于利用分布在世界各地的数百个地震台记录的地震波绘制弹性属性图。所有用于成像地球深处的计算工具和技术都是近似的，作为所谓的地震层析成像结果的模型的准确性和精确度存在很大的不确定性。该项目使用使用高精度计算机代码和规定的地球结构生成的合成数据集，以及使用合成数据对内部结构进行成像的标准分析技术。通过比较规定的地球结构和恢复的地球结构，可以对常见分析技术的真实分辨率进行调查和量化。该项目旨在为不同技术的适用性和局限性制定指导方针。使用谱元素方法为一套具有不同弹性和滞弹性特征的地球模型生成大量长周期地震记录数据集。地震和地震台的真实分布被用来模拟真实条件，地震机制直接从数据中确定。表面波传播异常是用标准技术从数据中测量出来的，并根据地球结构采用不同程度的理论和计算复杂性的方法来解释异常。特别是比较了射线理论、二维和三维Born散射方法在不同三维地球模型下的性能。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This project involves an investigation of different technical approaches used to image the Earth's interior. Much of what is known about the structure, composition and temperature of the deep Earth comes from mapping of elastic properties using seismic waves from earthquakes recorded on hundreds of seismic stations distributed worldwide. All of the computational tools and techniques used to image the deep Earth are approximate, and significant uncertainty exists concerning the accuracy and precision of models that are the result of so-called seismic tomography. This project uses synthetic data sets, generated using a highly accurate computer code and a prescribed Earth structure, and standard analysis techniques to image the interior structure using the synthetic data. Comparison of the prescribed and recovered Earth structures allows the true resolution of common analysis techniques to be investigated and quantified. The project aims to develop guidelines for the applicability and limitations of different techniques.Large data sets of long-period seismograms for a suite of Earth models with different elastic and anelastic characteristics are generated using the spectral-element method. Realistic distributions of earthquakes and seismic stations are used to mimic real conditions, and earthquake mechanisms are determined directly from the data. Surface-wave propagation anomalies are measured from the data with standard techniques, and the anomalies are interpreted in terms of Earth structure employing methods of different levels of theoretical and computational complexity. In particular, the performance of ray theory and two-dimensional and three-dimensional Born scattering approaches are compared for different three-dimensional Earth models.