基于接收函数波形反演方法的青藏高原东北部地壳速度结构和各向异性研究

项目名称： 基于接收函数波形反演方法的青藏高原东北部地壳速度结构和各向异性研究

项目编号： No.41474066

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 天文学、地球科学

项目作者： 徐强

作者单位： 中国科学院青藏高原研究所

项目金额： 90万元

中文摘要： 青藏高原东北部的岩石圈变形机理仍然存在较大的争议，具有代表性的观点为刚性块体的东向挤出和俯冲、下地壳管道流模型等。解决存在的这些争议需要我们确定下地壳是否存在软弱层并且发生流动变形。地壳软弱层在地震学上一般对应着壳内低速异常区，而地震各向异性参数可以提供地壳是否存在流动变形的相对直接的证据。本项目利用位于青藏高原东北部新近布设的跨祁连山剖面,美国IRIS台站和区域固定台网记录的地震波形数据，开展以下2个方面的研究：1）利用P波接收函数和瑞利波相速度频散数据联合反演地壳S波速度结构，揭示壳内低速异常（存在的话）在不同块体之间的几何形态以及所表征的构造意义。这种联合反演方法明显优于单一观测资料的反演，降低了结果的非唯一性。2）利用P波接收函数波形随后方位角变化的特征反演地壳各向异性模型；阐明各向异性参数与地壳变形之间的响应关系。预期的研究结果为理解青藏高原岩石圈变形机理提供新的地震学的证据。

中文关键词： P波接收函数；波形反演；青藏高原东北部；地壳速度结构；各向异性

英文摘要： The mechanism of the lithospheric deformation beneath northeastern Tibetan plateau is still debated, with rigid-block eastward extrusion and subduction and lower-crustal channel flow model representing popular end-members.In order to address the above controversy, it requires us to verify there exists the flow of a weak lower crust.The weak materials are generally characterized by low seismic shear wave velocity,and crustal anisotropy parameters provide a realitively direct link with the deformational style. By analysing the seismic data recorded by the recently deployed Qilianshan profile, IRIS and regional permanent stations in northeastern Tibetan pleateau, this study concentrates on two aspects as follows: 1. obtain the crustal shear wave velocity structure by the joint inversion of the P receiver function and Rayleigh wave phase velocity dispersion data, which is helpful to indicate the the geometrical features of the low-velocity zones （if they exist） among different blocks and their tectonic implications. An advantage of the joint inversion method is that the nonuniqueness of individual receiver function or surface wave inversion is highly reduced. 2. determine the crustal anisotropy parameters based on receiver function waveform inversions, which can contribute to reveal the response relationship between anisotropy parameters and crustal deformation.The expected results provide new seismic evidences for understanding the mechanism of the lithospheric deformation of Tibetan plateau.

英文关键词： P receiver function;Waveform inversions;Northeastern Tibetan plateau;Crustal velocity structure;Anisotropy