Seismic activation of moderate-size earthquakes for the 1999 Chi-Chi, Taiwan, earthquake has been found. A self-organizing spinodal (SOS) model can explain some observations concerning seismic activation, but the equal time durations of the mid and precursory periods during an earthquake cycle conjectured in the original, published, SOS model have not been supported in this case. The Chi-Chi test presented here shows unequal time durations of the mid and precursory periods of an earthquake cycle. This, in turn, makes the possibility of time prediction of a characteristic earthquake impossible in the context of the SOS model. In addition, comparisons with numerical simulations of the sliding-block model suggest the change in the system's stiffness is a potential mechanism of seismic activation.