Nevertheless, in earthquake prediction research long-range correlations are often regarded as counterintuitive, probably on the ground that in a wide class of simple elastic models redistribution of stress and strain after an earthquake would be confined to the vicinity of its source (Saint Venant principle). This argument is not applicable to a media with microinhomogenuities, including the lithosphere, where the loss of strength (damage) and the change of stress propagate not by entirely elastic mechanisms (e.g., see ref. 57). Moreover, redistribution of stress may be not relevant to this argument, since the earthquakes involved in long-range correlations may not trigger each other but reflect an underlying large-scale process such as microfluctuations in the movement of tectonic plates (9) or of crustal blocks within fault zones (18), migration of fluids (4), and perturbation of the ductile layer beneath the seismically active zone (58). Accordingly, there is no reason to look for premonitory phenomena only near an incipient fault break.
Unexplored Possibilities. Unexplored possibilities to develop the next generation of prediction algorithms seem to emerge, supported by the models reproducing the dynamics of seismicity (e.g., see refs. 2, 3, and 15–22), by abundance of relevant observations still not explored with adequate scaling and apart from that by a large collection of failures to predict, false alarms and successful predictions (e.g., see refs. 12, 13, 27, 28, 31, and 37). The algorithms described here may not use the most optimal sets of premonitory patterns and of the values of adjustable parameters, so that both sets can be possibly optimized. More fundamental possibilities can be enumerated as follows.
To consider premonitory phenomena separately inside and outside the potential nucleation zones of strong earthquakes. Such zones are formed around some fault junctions (30). Thus, as suggested in (59), some false alarms can be identified by high activity near these junctions.
To use for prediction the kinematic and geometric incompatibilities of the movements in a fault system (60, 61), reflecting its instability as a whole. In this way one may integrate the data on seismicity, creep, strain, GPS, and possibly on the migration of fluids.
To integrate different stages of prediction, following the singular experience of prediction of the Haicheng earthquake in China, 1976 (62).
While the performance of the algorithms described here is modest, only a small fraction of the wealth of unexplored possibilities has been made use of.
This paper was written when I was a visiting professor in the Department of the Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology. I am very grateful to V. Kossobokov, I.Rotwain, M.Simons, F.Press, T.Jordan, A.Gabrielov, P.Molnar, Ch.Marone, and L.Knopoff for discussions, important suggestions, and highly relevant preprints. Ms. Z.Oparina provided patient and competent help in preparation of the manuscript. The studies reviewed in this paper were partly supported by the following grants: International Sciences Foundation (MB3000; MB3300), U.S. National Science Foundation (EAR 94 23818), International Association for the Promotion of Cooperation with Scientists from the Independent States of the Former Soviet Union (INTAS-93–809), Russian Foundation for Basic Research (944–05–16444a), and United States Geological Survey (under the Cooperation in Environment Protection, area IX).
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