A Fully Three-Dimensional Tomography Study of Upper Mantle Structure Beneath Eastern Asia

在该提案中，PI计划对东亚地幔各向异性剪切波速度进行区域三维（3-D）层析成像。这项研究将利用东亚大部分地区广泛分布的中等规模（5-6级）地震、越来越多的常设地震台站和区域层析成像方法的最新发展来进行。反演的数据将包括在面波、地幔翻转体波和ScS混响的中期（20- 100秒）三分量地震记录上测得的与频率有关的走时和振幅扰动。此外，这些测量获得的区域，中期地震波将使用准确和现实的全三维Frechet内核计算正常模式耦合算法反演。模型参数包括三维径向各向异性剪切波速度和上地幔过渡带不连续面的地形。在所研究区域的大部分地区，上地幔结构将在约500公里的水平尺度和约100公里的垂直尺度上得到解析。影响层析成像模型的问题，如源接收器的覆盖范围，反演程序，速度地形权衡，各向异性和衰减将被检查。这是全三维区域层析成像方法在大陆地区的首次应用。这也是第一个研究中，在速度和不连续地形的扰动联合反演。研究结果将为东亚地区的动力学演化及其与周边构造区的关系提供制约。更广泛的影响：PI与研究生密切合作，相关的区域层析成像研究和方法以及数据和软件也将提供给更广泛的地震学界。这里开发的技术可以成为其他区域层析成像研究的理想选择，例如USAray下的地幔结构。

ZhaoEAR-0308403In this proposal, the PI plans to conduct a regional three-dimensional (3-D) tomography for the anisotropic shear-wave velocity in the mantle beneath Eastern Asia. This study will be carried out by taking advantage of a wide distribution of moderate-sized (magnitude 5-6) earthquakes in most parts of Eastern Asia, an increasing number of permanent seismic stations and the latest developments in the methodology for regional tomography. The data to be inverted will include the frequency-dependent travel-time and amplitude perturbations measured on intermediate-period (20-100s) three-component seismic records of surface waves, mantle-turning body waves and ScS reverberations. Moreover, these measurements obtained from regional, intermediate-period seismic waves will be inverted using accurate and realistic full 3-D Frechet kernels computed by a normal-mode coupling algorithm. The model parameters will include the 3-D radially-anisotropic shear-wave velocity and the topographies of the upper-mantle transition-zone discontinuities. In most parts of the region under study, the upper-mantle structure will be resolved on a horizontal scale of ~500 km and a vertical scale of ~100 km. Issues affecting tomography models, such as source-receiver coverage, inversion procedures, velocity-topography trade-off, anisotropy, and attenuation will be examined. This is the first application of full 3-D regional tomography approach to a continental region. It is also the first study in which the perturbations in velocity and discontinuity topography are jointly inverted. The results will provide constraints for the geodynamic evolution of Eastern Asia and its relation to surrounding tectonic regions. Broader impact: The PI works closely with graduate students on this and related regional tomography studies and methods and data and software will also be made available to the wider seismology community. The techniques developed here can be an ideal choice for other regional tomography studies, for example the mantle structure under the USArray.--