In recent years, however, we see a revival of interest in prediction research at several fronts in a more subdued manner but rooted on more solid scientific ground. First, sufficient data began to accumulate for testing the validity of certain prediction methods and hypotheses underlying them. It is essential for a healthy development of earthquake prediction research to formulate a prediction method testable by others. Another trend is the increasing use of probabilities in communicating earthquake information to the public. Instead of predicting the time, place and magnitude of a future earthquake, recent public-policy documents attempt to estimate an earthquake probability in a given window of time, space and magnitude.
Probability is a relatively new concept in human history.
The concept appears to be useful in dealing with difficult problems in human society. In recent years, several earthquake predictions made officially by the U.S. Geological Survey were in terms of probabilities. A central issue in these attempts is whether the complex behavior of seismicity is caused by the non-linear dynamics inherent to earthquake rupture or by the interaction of rupture with heterogeneities of fault zone structure.