Seismic Observations from the Random Wavefield: A New Tool for High-Resolution Seismology in the Context of EarthScope

0450082 Ritzwoller拟议的研究将推进和应用一种新的面波层析成像方法的基础上测量的面波色散是独立的地震发生。该方法基于通过互相关形成随机地震波场的一部分的环境或背景地震噪声序列来提取表面波绿色函数。在美国境内不同距离的台站的概念验证实验表明，用这种方法进行的色散测量是可重复的，并再现了地震后弹道波上获得的传统测量所提供的信息。基于噪声的面波测量使我们能够构建加州下方主要地质单元的层析成像图像，低速异常对应于主要沉积盆地，高速异常对应于主要山脉的火成岩核心。这种方法可以提高分辨率和逼真度的地壳图像从面波分析，特别是在大陆尺度阵列的背景下，如USARAY组成部分的EarthScope，其中许多站间的面波测量承诺集中地震图像和模型的地壳和上地幔下的美国。拟议的工作有两个主要目标。第一个目标是增进对背景地震噪声的了解，并继续发展一种可靠的方法，通过两个台站的互相关测量面波频散。第二个目标是将该方法应用于模拟和新兴的USARAY数据。分析将集中在三个空间尺度：（1）大陆尺度，类似于USARAY的永久部分，使用美国国家地震网（USNSN）和全球地震网（GSN）的数据，以及新兴的高级国家地震系统（ANSS）的宽带部分;（2）区域尺度，类似于USARAY的可移动部分，使用来自加州和落基山脉的宽带阵列的数据;和（3）局部尺度，类似于USARAY和PASSCAL实验的柔性组件的部署，使用来自南加州和黄石地区的阵列的数据。

0450082RitzwollerThe proposed research will advance and apply a new method of surface-wave tomography based on measurements of surface wave dispersion that are independent of earthquake occurrence. The method is based on the extraction of surface-wave Green functions by cross-correlating sequences of ambient or background seismic noise that form part of the random seismic wavefield. Proof-of-concept experiments for stations separated by various distances within the US demonstrate that dispersion measurements made with this method are repeatable and reproduce information provided by traditional measurements obtained on ballistic waves following earthquakes. Noise-based surface- wave measurements allow us to construct tomographic images of the principal geological units beneath California, with low-speed anomalies corresponding to the main sedimentary basins and high-speed anomalies corresponding to the igneous cores of the major mountain ranges. This method can improve the resolution and fidelity of crustal images obtained from surface-wave analyses, in particular, in the context of a continental scale array such as the USARRAY component of EarthScope, where numerous inter-station surface-wave measurements promise to focus seismic images and models of the crust and upper mantle beneath the US. The proposed work has two principal objectives. The first is to improve understanding of background seismic noise and to continue to develop a robust method to measure surface-wave dispersion from two-station cross-correlation. The second objective is to apply the method to analog and emerging USARRAY data. Analysis will concentrate on three spatial scales: (1) continental-scale, analogous to the permanent component of USARRAY, using data from the US National Seismic Network (USNSN) and the Global Seismic Network (GSN), as well as the broad-band component of the emerging Advanced National Seismic System (ANSS); (2) regional-scale, analogous to the transportable component of USARRAY, using data from broad-band arrays in California and the Rocky Mountains; and (3) local-scale, analogous to deployments of the flexible component of USARRAY and PASSCAL experiments, using data from arrays in Southern California and the Yellowstone areas.