Abstract: This paper gives the real-time SEM observation of subcracks' characteristics and their development with loading around en echelon fractures in uniaxially compressed marble plate specimen. The influences of the length of fracture, amount of separation and overlap between the prefabricated en echelon fractures on the subcracks' development are analysed based on phorographs taken during the experiment. The result shows that the interaction between en echelon fractures becomes stronger with less amount of separation. When the amount of separation is less than the fracture length, the number of the subcracks in between area of en echelon fractures will increase with the overlap between the fractures, corresponding to a certain amount of separation. Finally, the test results are compared with the special-temporal development of ground water anomaly and earthquake series before Haicheng earthquake.

Key words: earthquake precursor, en echelon fractures, Haicheng earth-quake, subcracks development

摘要： 对含两条雁行排列预制割缝的大理岩平板试件进行了单轴压缩实验，用扫描电镜实时观测了割缝周围次级裂纹随外载增加而发育及变化的过程，研究了割缝长度、两条割缝的间距及重叠度对次级裂纹发育特征的影响。结果表明：两条割缝之间的间距越小，相互作用越强，间距等于预制割缝长度时，一条割缝周围的次级裂纹发育便基本上不受另一条割缝的影响。当存在相互作用时，割缝之间区域中次级裂纹的条数随着两条割缝的间距的减小和重叠度的增加而增加。将次级裂纹的发育与海城地震前地下水位异常作了对比，发现两者的时空变化特征颇为相似，据此反推了海城地震断裂和活动断裂的相对空间几何展布及时间演化序列。

关键词: 地震前兆, 雁行断裂, 次级裂纹发育, 海城地震