关键词: 地震前兆, 雁行断裂, 次级裂纹发育, 海城地震

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