Cannot Earthquakes be Predicted?

Wyss, Max; Aceves, Richard; Park, Stephen; Geller, Robert; Jackson, David; Kagan, Yan; Mulargia, Francesco

Geller et al. (1) present an unduly negative view of research in a difficult field. At present, no mechanism for the cause of electromagnetic precursors is known well enough so that these precursors can be used reliably for earthquake prediction (2). Within the framework of the scientific method, however, refinement of a hypothesis in earthquake prediction becomes a multiyear process with infrequent experiments (that is, observations associated with earthquakes). This is the reason why most reports of precursors are written after the earthquake has occurred. It is time for earthquake prediction research to be more honestly identified as earthquake monitoring. Part of the problem is of our own making; some of us in the field have been overly quick to promise viable prediction techniques and equally quick to declare prediction experiments failures. Had we been more patient in the 1980s, monitoring such experiments as that in Hollister, California, we might have recorded the 1989 Loma Prieta earthquake, and experiments in Palmdale, California, might have caught the 1994 Northridge earthquake. The length of an experiment should not be an argument against the potential value of the eventual results. Not only do efforts to detect these precursory changes continue in both the United States (3) and internationally (4), but contrary to the statements by Geller et al., the VAN experiment (5) is still being actively debated and considered as a viable prediction tool. The key to assuring that these experiments are valuable is to design them to objectively define anomalies, differentiate between natural signals and noise, elucidate physical mechanisms, and provide a data set amenable to statistical analysis. The answer to whether or not earthquakes can eventually be predicted depends on how one defines the acceptable level of uncertainty associated with prediction. The field is not yet sufficiently mature to address the uncertainty in most cases. We simply have not had sufficient numbers of events to establish a cause-and-effect relationship, much less assess uncertainty or identify a physical mechanism. Whether or not a particular level of uncertainty is useful must be judged by those entrusted with public safety and decision making. Geller et al. say that the previous 100 years of failure at prediction is an argument against future success. However, geophysically based prediction techniques are still only a few decades old, and they introduce fundamentally new and different approaches from the previous 100 years. Although we agree that earthquake hazard mitigation is more valuable in the immediate future, dismissing the field of earthquake prediction research seems premature to us. If one considers the potentially large payoff that can be realized from a successful prediction, and that at least one technique (VAN) is still being actively evaluated, one would have to conclude that earthquake prediction research should be continued and the debate left open.

Cannot Earthquakes be Predicted?

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