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。该项目涉及对用于地球内部成像的不同技术方法的调查。关于地球深部的结构、组成和温度的大部分知识来自于利用分布在世界各地的数百个地震台站记录的地震波绘制的弹性特性图。用于对地球深部进行成像的所有计算工具和技术都是近似的，在所谓的地震层析成像所产生的模型的准确性和精确度方面存在很大的不确定性。该项目使用合成数据集，这些数据集是使用高度精确的计算机代码和规定的地球结构生成的，并使用标准分析技术，利用合成数据对内部结构进行成像。规定的和恢复的地球结构的比较允许真正的解决方案的共同分析技术进行调查和量化。该项目旨在为不同技术的适用性和局限性制定准则，利用谱元法生成一套具有不同弹性和滞弹性特性的地球模型的长周期地震图的大数据集。地震和地震台站的真实分布被用来模拟真实的条件，地震机制直接从数据中确定。面波传播异常测量的数据与标准技术，并解释异常的地球结构，采用不同层次的理论和计算复杂性的方法。特别是，射线理论和二维和三维玻恩散射方法的性能进行了比较，为不同的三维地球模型。

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.