青藏高原东北缘地壳地震各向异性研究进展

Reviews on the Crustal Seismic Anisotropy in the Northeast Margin of the Tibetan Plateau

摘要:

青藏高原东北缘是青藏块体与华北块体的接触前缘部位,是研究青藏高原隆升扩张和深部动力学问题的重要区域。本文收集了青藏高原东北缘及其邻区由不同方法和不同资料获得的地壳地震各向异性结果,介绍了中上地壳和全地壳各向异性特征;结合区域地质构造、地表运动、构造应力和深部结构,分析了研究区域地壳各向异性的区域分布特征及其与地质构造的关系。结果表明,青藏高原东北缘地震各向异性存在明显的横向区域差异性,体现区域深部构造和地壳介质变形的复杂性;上地壳与全地壳的垂向差异性,反映出该区域可能存在各向异性分层现象。由于青藏高原隆升在其东北缘的伸展边界、物质运移及深部动力模式等尚处在探讨之中,结合多种数据并综合多种方法分析,有助于获得精细、准确的地震各向异性信息,为研究青藏高原隆升演化机制和深部动力模式提供有效的约束。

Abstract:

The northeastern margin of the Tibetan Plateau is the border between the Tibetan block and the north China block,which is an important area for studying the uplift expansion and deep dynamics of the Tibetan Plateau. In this paper,we summarize the previous results of crustal seismic anisotropy obtained by different methods and data from the northeast margin of the Tibetan Plateau and its adjacent areas,and introduce the characteristics of upper crustal and whole crustal anisotropy. Combining the regional geological structure,surface motion,tectonic stress and deep structure,we discuss the spatial distribution of crustal anisotropy and its relationship with geological structure. In the northeastern margin of the Tibetan Plateau,the lateral local variability of seismic anisotropy in the crust and the vertical variability between the upper crust and the whole crust,reveal the complexity of regional deep tectonics and crustal medium deformation. Our results show that there exist obvious lateral regional differences in seismic anisotropy,reflecting the complexities of tectonics and crustal deformation. The vertical differences between the upper crust and the whole crust imply the possibility of multiple layer anisotropy. Since the extensional boundaries,material transport and deep dynamics patterns of the uplift of the Tibetan Plateau at its northeastern edge are still not quite clear,it would be significant by combining multiple data and comprehensive analysis of multiple methods in order to obtain detailed seismic anisotropy patterns,and to provide effective constraints for the growth scenarios of the Tibetan Plateau.