非均质不连续介质三维构造应力场的光弹性实验研究

Photoelastic Experimental Study on the 3-D Tectonic Stress Field in Inhomogeneous and Noncontinuous Medium

一、引言已有的用光测弹性力学方法研究构造应力场成果多局限于二维空间。显然,这些成果没有考虑不同产状的断裂构造在地壳深处具有与地表完全不同的组合特点,更没有考虑地壳的分层性以及不同层位介质的非均一性。为使研究模型更逼近真实,我们以松潘震区为研究对象,先后进行了均质和非均质不连续三维光弹性实验研究,均质不连续介质的研究成果已经发表,本文侧重介绍非均质不连续介质的研究结果。为评价构造条件和介质条件在震源应力场形成中各自所起的作用,必要时还引用文献的资料进行比较分析。

Taking the Songpan earthquake region as our study area, we carried out an experimental study on the three—dimensional tectonic stress field in inhomogeneous and noncontinuous medium on the basis of the previous photoelastic modeling of the three-dimensional focal stress field in homogeneous and noncontinuous medium. This paper presents briefly the 3-D photoelastic method for studying the 3-D tectonic stress field in inhomogeneous medium, including the selection of the similarity conditions, the technique of model preparation, and the algorithm of calculation. The result of inhomogeneous and noncontinuous medium is elucidated in detail. We investigated the forming conditions of the focal stress field and its attenuation in 3-D space, the relationship between precursor-sensitive locations and the focal stress field, the effect of various tectonic and material factors on the characteristics of stress distribution. This experimental study is the first of the kind, nevertheless the result is verified by objective facts, indicating that the method is an effective means for studying the tectonic stress field and earthquake precursors.