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

在本研究中，中国太平洋研究所计划对东亚地幔各向异性横波速度进行区域三维层析成像。本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、越来越多的永久地震台站和区域层析成像方法的最新发展来进行。要反演的数据将包括在中期（20-100秒）三分量地震记录中测量到的频率相关的旅行时间和振幅扰动，这些地震记录包括表面波、地幔转向体波和南海混响。此外，这些从区域中期地震波中获得的测量数据将使用由正模耦合算法计算的精确和真实的全三维Frechet核进行反演。模型参数将包括三维径向各向异性横波速度和上地幔过渡带不连续面地形。在研究区域的大部分地区，上地幔结构将在~500 km的水平尺度和~100 km的垂直尺度上得到解析。影响断层扫描模型的问题，如源-接收器覆盖，反演程序，速度-地形权衡，各向异性和衰减将被检查。这是首次将全三维区域断层扫描方法应用于大陆区域。这也是第一次将速度扰动和不连续地形扰动联合反演的研究。研究结果将为东亚的地球动力学演化及其与周边构造区的关系提供约束条件。更广泛的影响：PI与研究生密切合作，进行相关的区域断层扫描研究，方法、数据和软件也将提供给更广泛的地震学社区。这里开发的技术可以成为其他区域断层扫描研究的理想选择，例如usarray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.--