Crustal and Uppermost Mantle Anisotropy Beneath Tibet: New Constraints on Deformation

PIS将把地震面波层析成像的创新应用于中国迅速扩大的宽带地震数据集，以构建西藏大部分地区下方和周围地壳和最上地幔内部的径向和方位各向异性的三维模型。新的层析成像方法包括环境噪声层析成像和基于阵列的地震层析成像，它们承诺对研究区域大部分地区从浅地壳到地幔深度至少150公里、横向分辨率约100公里的同位素和各向异性结构产生新的结构约束。有针对性的数据集通过引入一个巨大的新数据资源--西藏周围的中国省级网络--来利用美国过去和正在进行的PASSCAL实验。这项工作将与中国国家科学院武汉大地测量与地球物理研究所的研究人员合作促进这项工作。初步的概念验证数据处理和反演工作建立了组成数据集的质量，并保证了整个西藏地壳和最上地幔的综合各向同性和各向异性模型的产生。这项工作的动机是获得与印度和亚洲大陆碰撞有关的基本问题的新见解，特别是印度和亚洲地幔岩石圈在碰撞中的作用，以及地壳如何对碰撞做出反应。对这些问题的详细考虑需要全西藏地壳和上地幔各向同性和各向异性地震变量的高分辨率三维模型。各向异性模型尤其将对地壳应变的垂直一致性提供新的约束，这将有助于解决地壳变形对大陆碰撞的反应的相互竞争的理论之间的争论。

The PIs will apply innovations in seismic surface wave tomography to burgeoningbroadband seismic data sets in China to construct a 3-D model of radial and azimuthal anisotropy within the crust and uppermost mantle beneath and surrounding much of Tibet. The new tomographic methods include ambient noise tomography and array-based earthquake tomography that promise new structural constraints on isotopic and anisotropic structures from the shallow crust to mantle depths of at least 150 km with a lateral resolution of about 100 kmacross most of the study region. Targeted data sets leverage past and on-going US PASSCAL experiments by introducing a vast new data resource, the Chinese provincial networks surrounding Tibet. This work will be facilitated by collaboration with researchers at the Institute of Geodesy and Geophysics of the Chinese National Academy of Sciences in Wuhan, China.Preliminary proof-of-concept data processing and inversion efforts establish the quality of the constituent data sets and guarantee the production of integrated isotropic and anisotropic models of the crust and uppermost mantle across all of Tibet.This work is motivated to gain new insight into fundamental questions related to the continental collision between India and Asia; in particular, the role of the Indian and Asian mantle lithospheres in the collision and how the crust deforms in response to the collision. Detailed consideration of these questions requires high resolution 3D models of isotropic and anisotropic seismic variables in the crust and uppermost mantle across all of Tibet. Anisotropic models especially will provide new constraints on the vertical coherence of strains in the crust that will help resolve debate between competing theories of crustal deformation in response to continental collision.