Prevention of strong earthquakes: Goal or utopia? |
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Authors: | Sh A Mukhamediev |
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Institution: | 1.Institute of Physics of the Earth,Russian Academy of Sciences,Moscow,Russia |
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Abstract: | In the present paper, we consider ideas suggesting various kinds of industrial impact on the close-to-failure block of the
Earth’s crust in order to break a pending strong earthquake (PSE) into a number of smaller quakes or aseismic slips. Among
the published proposals on the prevention of a forthcoming strong earthquake, methods based on water injection and vibro influence
merit greater attention as they are based on field observations and the results of laboratory tests. In spite of this, the
cited proofs are, for various reasons, insufficient to acknowledge the proposed techniques as highly substantiated; in addition,
the physical essence of these methods has still not been fully understood. First, the key concept of the methods, namely,
the release of the accumulated stresses (or excessive elastic energy) in the source region of a forthcoming strong earthquake,
is open to objection. If we treat an earthquake as a phenomenon of a loss in stability, then, the heterogeneities of the physicomechanical
properties and stresses along the existing fault or its future trajectory, rather than the absolute values of stresses, play
the most important role. In the present paper, this statement is illustrated by the classical examples of stable and unstable
fractures and by the examples of the calculated stress fields, which were realized in the source regions of the tsunamigenic
earthquakes of December 26, 2004 near the Sumatra Island and of September 29, 2009 near the Samoa Island. Here, just before
the earthquakes, there were no excessive stresses in the source regions. Quite the opposite, the maximum shear stresses τmax were close to their minimum value, compared to τmax in the adjacent territory. In the present paper, we provide quantitative examples that falsify the theory of the prevention
of PSE in its current form. It is shown that the measures for the prevention of PSE, even when successful for an already existing
fault, can trigger or accelerate a catastrophic earthquake because of dynamic fault propagation in the intact region. Some
additional aspects of prevention of PSE are discussed. We conclude that in the near future, it is too early to consider the
problem of prevention of a forthcoming strong earthquake as a practical task; otherwise, the results can prove to be very
different from the desired ones. Nevertheless, it makes sense to continue studying this problem. The theoretical research
and experimental investigation of the structure and properties of the regions where the prevention of a forthcoming strong
earthquake is planned in the future are of primary importance. |
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