藏南Doublet构造的精细结构及其空间变化规律

Collision of Indian plate and Eurasian plate created the Tibet plateau. In southern Tibet, a structure named “Doublet” was observed by P receiver function. The Doublet is a kind of curst structure characterized by two discontinuities at 60km and 80km depth respectively. This phenomenon could be traced from north of Yarlung-Tsangpo suture to N31° through common conversion point (CCP) technique. Previous studies suggested it might be explained as partially eclogitized Indian lower crust. This knowledge might be misleading from view of the receiver function method. Here we develop a semi-automatic joint inversion technique of receiver function and travel time residuals. By applying this technique to data available (public station on IRIS and ANTILOPE-1,2), fine structures of the Doublet are obtained. We further studied the formation mechanism of the Doublet and inferred the crust-thicken and collision model of Tibet.

在藏南，P波接收函数揭示了一个被称之为Doublet的构造，表现为地壳内60km和80km附近分别存在一个速度递增的界面。通过共转换点叠加成像的研究显示Doublet构造南起雅鲁藏布缝合带，北至N31°附近。一般认为80km为Moho面，两个界面之间的地壳可能已经部分榴辉岩化，但精细结构研究不够。本项目拟利用IRIS公开台站和ANTILOPE-1,2地震台站的波形数据，通过一种半自动化的P波接收函数和相对走时残差联合反演方法计算出Doublet构造的两个界面的深度和界面之间的下地壳的速度，从而确定Doublet构造的性质。利用上面的结果作为约束，用线性方法反演P波接收函数波形，以验证结果的可靠性。分析不同空间位置的Doublet构造的差异以及方位各向异性，尝试从整个拉萨地块的角度解释Doublet构造及其差异的成因，进而探讨藏南地壳的增厚机制和印度板块俯冲模式。