Abstract: Applying fractal theory, using Enlarged Box Algorithm, the authors calculate the multi-fractal spectrums of thetem poral distribution of earthquakes in North China from 1960 to 1982. It is found that several earthquakes (suchas Tang shan 1976 earthquake) have all displayed themselves dramatically in the spectrums. In the years when the big earthquakes happen, D_q values of negativeq increase greatlyor D_q values of positiveqdecrease greatlyor both happen. The result may be useful for earthquake prediction. We also analy ze after shock sequences of the four great earthquakes (Xingtai 1966, Bohai 1969, Haicheng 1975, Tang shan 1976), calculate the multi-fractal spectrums of their spatial distribution which varies with time, finding that multi-fractal spectrums change greatly with in the earthquakesequence as time goes. Something meaningful has been found by com paring theperformance of the spectrums of the four earthquakesequences.

Key words: North China earthquake, Multi-fractal, Enlarged Box Algorithm, temporal and special change