A time series of acoustic emissions (AE) in basalt was measured under constant uniaxial compression. Some bursts of AE events considered to be the main shock and aftershock sequences were observed. Two models describing the aftershock sequences (the exponential decay model, n(t)=K exp (-pt), and the Omori's power law model, n(t) = K/(c+t)p, where n(t) denotes the occurrence rate of aftershocks at time t) were examined. With the progress of the fracturing process, the bursts changed from the exponential decay type to Omori's power law type, and the p value of Omori's power law aftershock sequences decreased. These results indicate that microfracturing gains a longer tail with the evolution of the fracture process. The reproduction of Omori's power law aftershock sequences of AE events suggests that the self-similarity of rock fracturing holds good over a range from microfracturing to large earthquakes. ¿American Geophysical Union 1987