多种地震方法探测青藏高原东北缘地壳上地幔结构的研究进展

The research progress of the detection crustal and upper mantle structure of northeastern Tibetan Plateau by multiple seismic methods

青藏高原东北缘地区在地形上处于青藏高原隆起区的东北边缘,青藏高原块体、鄂尔多斯块体和阿拉善块体交汇于此,是整个高原向大陆内部扩展的前缘部位,也是其最新的和正在形成的高原重要组成部分.区域内新生代构造变形和地震活动强烈,是研究青藏高原隆升、构造变形,探讨强地震发生的深部环境的最佳场所.为研究青藏高原东北缘地壳上地幔深部结构构造特征,近些年来开展了大量的地球物理探测工作.笔者收集了近三十年来在青藏高原东北缘展开的人工地震和天然地震观测工作,综合论述了人工源地震探测方法和天然地震成像方法(主要包括接收函数方法、地震层析成像方法、SKS剪切波分裂分析等)的发展和不同地震探测方法所取得的关于青藏高原东北缘壳幔速度结构、莫霍面形态、地壳上地幔各向异性研究等所取得的成果,总结分析了青藏高原东北缘地壳上地幔结构特征方面已达成的的一致观点以及有待进步一研究之处,并对比分析了不同方法之间的差异之处.

The study area is located in the northeastern Tibetan Plateau uplift zone where the Tibetan Plateau, the Ordos Block and the Alashan Block intersect. The northeastern Tibetan Plateau is the front part of the plateau internal extension to mainland, as well as the latest and forming important part of the plateau. The northeastern Tibetan Plateau, where strong Cenozoic tectonic deformation and earthquake activities occurred, is the best place to study the plateau uplift, tectonic deformation, and the deep environment of strong earthquake. A large amount of geophysical exploration work has been conducted in the northeastern Tibetan Plateau to study the crustal and upper mantle structure. This paper collects the seismic results from active source data and earthquake data in the northeastern Tibetan Plateau in the recent 30 years and summarizes the crust-mantle structure, composition, deformation and dynamics in the northeastern Tibetan Plateau. Finally, the authors discuss comprehensively about the crustal and upper mantle velocity structure, the Moho interface and anisotropy pattern in the northeastern Tibetan Plateau by comparing the results obtained from different seismic methods （including deep seismic sounding, receiver function, seismic tomography and shear wave splitting ）. The studies have reached a consensus view of the overall trend of the crustal thickness, the crustal Poisson＇s ratio, the significant lateral heterogeneity in the mantle and anisotropy in the northeastern Tibetan Plateau. After decades of hard work, the seismic observations in the northeastern Tibetan Plateau have made considerable progress, the results obtained from different research methods in the study area have provided a strong geophysical evidence for the deep structure of the Tibetan Plateau. However, due to the restricted geographical conditions, the existing research work in the northeastern Tibetan Plateau is still relatively limited, some results still exist significant differences. It is necessary to combine different geophysical data and methods to expand the further studies in the northeastern Tibetan Plateau, and conduct comparative studies with different boundaries of the northeastern Tibetan Plateau.