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  • As we all agree that we know little about how earthquakes initiate and how to predict them, it follows that we will study the problem and eventually reach a relatively satisfactory solution. The question is, will we do it with the significant financial support and expedience this humanitarian effort deserves, or will we force individual scientists to do it in their non-existent spare time?

    • Max Wyss
    Debate
  • Wyss's letter in week 5 of this debate claims that I made a 'significant error' in my week 3 article. I explain here why this claim should not be accepted, placing my rebuttal in a more general context.

    • Robert J. Geller
    Debate
  • Testing hypothesises is an essential part of earthquake prediction. The 'game rule' associated with this test is especially important because it leads to the criteria for accepting or rejecting a statistical hypothesis related to earthquake prediction.

    • Zhongliang Wu
    Debate
  • All discussions so far have referred (perhaps not surprisingly) to the properties of earthquakes, their times, locations, nucleation mechanisms, physics of the source, possible precursors, etc. I think this will lead nowhere. Earthquakes are extraordinarily varied and impossible to average. Perhaps the only feature of earthquakes that can be relied on is that they release a large amount of stress which, because rock is weak, has necessarily accumulated over a large volume of rock. If this build up of stress can be monitored then the time and magnitude of the earthquake when fracture criticality is reached can be subject to 'stress-forecast'. I suggest that we already know how to do this. The effects have been seen with hindsight for eight earthquakes worldwide, and the time and magnitude of an M=5 earthquake has been successfully stress-forecasted.

    • Stuart Crampin
    Debate
  • Scholz omitted crucial parts of the the recent history of the seismic gap forecast and test. He remarked that our test of the gap theory was 'flawed' because it used earthquakes 'smaller than system-sized'. This was also asserted in a published comment by Nishenko & Sykes1 and answered by Jackson & Kagan2. But 'system-sized' was never defined in the original seismic gap model3.

    • David Jackson
    Debate
  • Earthquake prediction is strictly related to empirical precursors. Despite the results presented in recent decades in support of the existence of empirical precursors there is scepticism in the scientific community about whether they exist1-3. The widespread argument is that precursor signals reported are unrelated to earthquake activity and that they could have occurred by chance. If this were true, earthquake prediction would not be possible.

    • Francesco Biagi
    Debate
  • Wyss asserted that without funding at "a scale comparable to the funding of astrophysical research ... serious progress toward learning how to predict earthquakes" was impossible. However, extensive prediction efforts in several countries in several eras have all failed. Further allocation of public funds appears unwarranted unless there are specific and compelling grounds for thinking that a proposed new prediction programme will be successful.

    • Robert J. Geller
    Debate
  • As anyone who has ever spent any time in California can attest, much public attention is being focused on the great earthquake-prediction debate. Unfortunately, this attention focuses on deterministic predictions on the day-to-week timescale. But as some of the participants in this debate have pointed out1,2 current efforts to identify reliable short-term precursors to large earthquakes have been largely unsuccessful, suggesting that earthquakes are such a complicated process that reliable (and observable) precursors might not exist. That is not to say that earthquakes do not have some 'preparatory phase', but rather that this phase might be not be consistently observable by geophysicists on the surface. But does this mean that all efforts to determine the size, timing and locations of future earthquakes are fruitless? Or are we being misled by human scales of time and distance?

    • David Bowman
    • Charles Sammis
    Debate
  • It is certainly possible to define the reliable prediction of individual earthquakes so narrowly that success is impossible. For instance, in Main's level 4 he refers to predictions with such precision and accuracy that a planned evacuation can take place. None of the contributors have yet to suggest that this is a possibility and I agree with Wyss that using this straw man as the standard will not lead to a useful debate. However, Main's levels 2 and 3 may lead to socially useful tools regardless of whether we call them predictions or probabilistic forecasts.

    • Andrew Michael
    Debate
  • For a prediction to be successful, the probability of occurrence in a time interval and a space domain must be specified in advance, as must the lower magnitude. There are two important additional constraints: a utilitarian constraint demands that the lower magnitude bound be appropriate to societal needs; in other words, we are especially interested in strong destructive earthquakes.

    • Leon Knopoff
    Debate
  • The contributions to the debate about earthquake prediction research in Nature so far, clearly show that we have hardly scratched the surface of the problem of how earthquake ruptures initiate and how to predict them. This arises from the difficulty of the problem and the lack of a vigorous program to study these questions. As Andrew Michael has said, funding for earthquake prediction research is a small fraction of the seismology program, in the U.S., and seismology is poorly funded compared to disciplines like astronomy.

    • Max Wyss
    Debate
  • One of this week's email contributors considers the consequences for earthquake predictions if they are indeed self-organized critical phenomena.

    • Per Bak
    Debate
  • The topic posed by the editors for this debate, is whether the reliable prediction of individual earthquakes is a realistic scientific goal. Translated into everyday language, this becomes: given the present state of the art, does earthquake prediction research merit a significant investment of public funds? My initial contribution to this debate stated the negative case. None of the other debaters appears to have made strong arguments for the affirmative.

    • Robert J. Geller
    Debate
  • The contributions to the debate about earthquake prediction research in Nature so far, clearly show that we have hardly scratched the surface of the problem of how earthquake ruptures initiate and how to predict them. This arises from the difficulty of the problem and the lack of a vigorous program to study these questions. As Andrew Michael has said, funding for earthquake prediction research is a small fraction of the seismology program, in the U.S., and seismology is poorly funded compared to disciplines like astronomy.

    • Max Wyss
    Debate
  • How well can we predict earthquakes? As suggested in Ian Main's introduction to this forum, we can easily predict the behaviour of populations of earthquakes and we clearly cannot completely predict the behaviour of individual earthquakes. But where is the boundary between the easy and the impossible? In search of this boundary let us take a tour through Ian Main's four levels of earthquake prediction.

    • Andrew Michael
    Debate
  • There has been a recent recrudescence1,2 of the long debate on the feasibility of short-term earthquake prediction, namely, the prediction, with a lead time of days to weeks, of the time, location and magnitude of a future event. This type of earthquake prediction is inherently difficult to research and has a chequered past, with many intriguing but fragmentary observations of possibly precursory phenomena but no scientifically based and verified successes3.

    • Christopher Scholz
    Debate
  • The recent earthquake in Colombia (Fig. 1) has once again illustrated to the general public the inability of science to predict such natural catastrophes. Despite the significant global effort that has gone into the investigation of the nucleation process of earthquakes, such events still seem to strike suddenly and without obvious warning. Not all natural catastrophes are so apparently unpredictable, however.

    • Ian Main
    Debate