High-Resolution Upper-Mantle Tomography Using Seismic Arrays and Full-Wave Frechet Kernels: Southern Africa

使用地震阵列和全波 Frechet 内核进行高分辨率上地幔断层扫描：南部非洲

• 批准号: 0125598
• 负责人: Li Zhao
• 金额: $ 16.41万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-01-01 至 2004-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0125598&HistoricalAwards=false
• 关键词: Resolution; Upper; Mantle; Tomography; Using

Zhao, LiThe focus of this proposal is to develop a high-resolution tomography method for seismic arrays. Resolution to sub-array structure is enhanced by inverting the phase and amplitude variations between adjacent stations, rather than at individual stations, in order to minimize biases caused by uncertainties in lateral heterogeneities far away from the array. Frechet kernels of the data are calculated by coupled normal-mode summation so that all finite-frequency effects are accounted for with no high-frequency or averaging approximations. A new traveling-wave method will also be developed to calculate exact kernels near stations. Asymptotic Legendre functions are used to express waves from the source to sub-array heterogeneity (scatterer), but exact Legendre functions are adopted for waves from the scatterer to the station.The tomography method is being developed for the Southern Africa Seismic Array, deployed to study the Kaapvaal craton, and 3-D inversions are conducted for upper-mantle anisotropic structure. Data are measured for surface and upper-mantle body waves at an average of 50 three-component stations from 51 teleseismic events. The result will shed new light on the conflicting features in some of the recent regional models, such as the presence of an oceanic-type low-velocity zone beneath the craton and shear-wave anisotropy. The multi-station, full-wave method developed here is also well suited to serve the need of the upcoming USArray. With its proposed average spacing of about 70 km between adjacent stations, this method will be able to provide a nearly uniform lateral resolution of about 50 km in the upper mantle over the entire continental United States.

本文的重点是发展一种高分辨率的地震台阵层析成像方法。子阵列结构的分辨率通过反转相邻站之间的相位和幅度变化而不是在单个站处的相位和幅度变化来增强，以最小化由远离阵列的横向不均匀性的不确定性引起的偏差。Frechet内核的数据计算耦合正常模式求和，使所有有限频率的影响占没有高频或平均近似。还将开发一种新的行波方法来计算台站附近的精确核。渐近勒让德函数用于表示从震源到子阵列异质性（散射体）的波，但从散射体到台站的波采用精确勒让德函数，正在为南部非洲地震阵列开发层析成像方法，部署该阵列研究卡普瓦尔克拉通，并对上地幔各向异性结构进行三维反演。在平均50个三分量台站的51个地震事件中测量了地表和上地幔体波数据。结果将揭示新的光在最近的一些区域模型，如克拉通和剪切波各向异性下的海洋型低速区的存在相冲突的功能。这里开发的多站全波方法也非常适合满足即将到来的USAray的需求。由于相邻台站之间的拟议平均间距约为70公里，这种方法将能够在整个美国大陆的上地幔中提供约50公里的几乎统一的横向分辨率。