关于岩石圈有效弹性厚度的地质理解

简要回顾了岩石圈均衡理论的发展及岩石圈区域均衡和挠曲理论在岩石圈动力学研究中起的作用,阐述岩石圈有效弹性厚度(Te)的概念和特征。强调Te的研究是地质学和地球物理学的紧密结合,即通过岩石圈挠曲理论和区域均衡原理,对地形和重力资料进行谱分析计算,来获取岩石圈的物理性质信息。计算的Te(和相应的挠曲刚度)是岩石圈等效的强度,与爆破地震、地震层析成像和大地电磁测深等方法观测到的岩石圈和地壳厚度不同,它们之间只有通过岩石圈的屈服刚度包络面(YSE)才能比较。大洋和大陆岩石圈YSE的理论计算,表明Te值显著小于地震学的地壳和岩石圈厚度。尤其对于大陆岩石圈,地壳厚度、热年龄和应变率均可显著影响岩石圈的强度。本文还以滇西为实例介绍了对相干值曲线计算的新认识和当前岩石圈Te研究的最新趋势。

GEOLOGICAL INTERPRETATION OF THE LITHOSPHERE EFFECTIVE ELASTIC THICKNESS

Lithosphere effective elastic thickness (Te) is a term on the bases regional isostasy and flexure theories of lithosphere. This paper firstly outlined the development of the isostasy, and then described the concept and characteristics of Te. It was emphasized that Te was a subject closely related to geology and geophysics since the Te was not only calculated by the spectrum analysis on the bathymetry and gravity data, also related to the geological, thermal, rheological structures. Te could provide us with the physical properties of lithosphere. However, Te merely was an equal and effective strength of lithosphere, and it could not be compared with the seismic and geo-electronic-magnetic thickness values of crust or lithosphere. But the yielding strength envelop (YSE) of lithosphere could compare the two kinds of thickness. The theoretical calculations of ocean and continental YSEs showed that the Te was obvious less that seismic thickness. Particularly, for the continent, the crust thickness, thermal age and strain rate significantly had strong effect on the lithosphere strength. Finally, taking western Yunnan as an example,the paper briefly introduced a new way to calculate the curve of coherence value to wave number, and discussed the latest progress of lithosphere Te.