The Parkfield Prediction Experiment failed, and the expected magnitude 6 earthquake still has yet to strike, even 6 years after the prediction window closed.
Such are the dangers in the field of earthquake forecasting. The main problem stems from the details of earthquake occurrence. There seems to be no single, universal method for recognizing the coming of an earthquake. While certain warning signs can occasionally be recognized, at other times these same warning signs fail to appear before an earthquake, or do appear but then are not followed by a large event. Thus, "prediction" becomes hit-and-miss (at best). That only makes it more difficult for the forecasters, since people tire of repeated false alarms of such a serious nature. The more often predictions prove wrong, the less likely the public is to heed the next one.
Probably the greatest challenge to
prediction efforts is to form forecasts the public will consider useful.
This means specifying the location, magnitude, and time with an
accuracy that makes preparation efficient and effective. Remember,
even the successful prediction at Haicheng almost failed because
people grew cold and tired of being outside for nine hours in the
wintertime. Had the predicted earthquake come a few hours later,
the effort might have been a failure in spite of its relative accuracy.
Imagine trying to suspend all the functions of a city like Los
Angeles for nine hours, awaiting an event many people doubt will
happen! Then imagine the uproar that would result should the predicted
event fail to occur. Predictions need to be accurate and dependable,
and that is simply beyond seismology's present ability to accomplish.
The accuracy of the Haicheng prediction was due in part to the identification of precursory phenomena, particularly foreshocks. If accurate earthquake forecasts are ever to become a reality, a dependable means of identifying precursory signs of an impending earthquake will need to be found. Are foreshocks a solution to this problem? Can they be recognized in advance of a mainshock?
