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。这个项目涉及对不同技术方法的调查，这些技术方法被用来对地球内部进行成像。我们对地球深处的结构、组成和温度的了解，大部分来自于全球数百个地震台站记录的地震地震波的弹性特性图。所有用于对地球深部成像的计算工具和技术都是近似值，在所谓的地震层析成像所产生的模型的准确性和精密度方面存在很大的不确定性。该项目使用合成数据集，这些数据集由高度精确的计算机代码和规定的地球结构生成，并使用标准分析技术使用合成数据对内部结构进行成像。将规定的和恢复的地球结构进行比较，可以对常用分析技术进行研究和量化。该项目旨在为不同技术的适用性和局限性制定指导方针。采用谱元法，对一套具有不同弹性和非弹性特征的地球模型生成了大数据集的长周期地震记录。地震的真实分布和地震台站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，并用不同理论和计算复杂度的方法从地球结构的角度解释这些异常。特别地，比较了射线理论和二维和三维玻恩散射方法在不同三维地球模型中的性能。

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.