Occurrence of a predicted earthquake on the San Andreas fault

In May 1985 we predicted¹ that an earthquake would occur on the San Andreas fault near Stone Canyon, California within a year. The prediction was based on the observation of seismic quiescence–defined as a significant decrease in the average occurrence rate of earthquakes within the source volume of the future mainshock. A mainshock of magnitude M_L = 4.6 occurred on 31 May 1986, rupturing exactly the specified segment of the fault. This is the first successful prediction of an earthquake along the San Andreas fault, and the probability to have come true by chance is