全球地震层析地幔密度横向不均匀及大陆动力学

地震层析为我们提供了研究全球及区域地幔横向不均匀的有力工具。本文使用Ｓ１２－ＷＭ１３［１］层析模型,假设地震波速度异常与密度异常之间呈线性关系［２］,以ＰＲＥＭ模型［３］为基础,计算了全球和部分区域的球谐展开１２×１２阶地幔密度异常分布;分析了一系列的结果,特别分析了大陆下部地幔密度异常的基本格局;讨论了其对大陆动力学研究的意义。应用于中国大陆发现,整个中国大陆下部７０ｋｍ－１５０ｋｍ深部范围内是地震剪切波的低速带或密度低的地区,而在１５０－４００ｋｍ范围中又处于密度高的异常地带。本文从地幔动力学的观念出发讨论了中国大陆岩石层构造运动的地幔动力学问题。

GLOBAL SEISMIC TOMOGRAPHY, THE DENSITY HETEROGENEITY OF THE MANTLE AND CONTINENTAL DYNAMICS

Seismic tomography gives us a important data set to investigate the density heterogeneity of the mantle. On this paper we calculate the density anomalies in the mantle by using Su et al's seismic tomography model S12-WM13[1] and the linear relationship between the velocity of seismic wavcform and density [2]. The basic density model is PREM model[3]. In order to understand the implications of these. calculation results we discuss the dynamical meaning of the" continental root" (or"mantle root"). We find that there is a lower density region in the depth 70-150km under the continent of China and thee is a higher density region in the depth 150-400km. This structure may be usful for us to understand and explain the dynamical ploblems of the continent and mantle of China.