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CNR: Alamanacco della Scienza

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N. 1 - 16 gen 2013
ISSN 2037-4801

International info   a cura di Cecilia Migali

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Earthquake and volcano: predictability vs crustal diagnosis

Several phenomena have been reported to be possibly associated with a subsequent strong earthquake. No simple compilation appears, however, to be enlightening. In addition, since the mechanisms are largely not understood, it appears awkward, if possible at all, to make any structured review of this apparently unsolvable problem. On the other hand, the tremendous tragedies, which almost every few years affect a large number of people, is such that every mere academic debate appears nonsense and ethically unacceptable.

Either for clarity or for 'simplicity' or for brevity purpose, the criterion that I followed has therefore been to attempt to assess some basic set of phenomena, which can be considered as a starting and reliable benchmark for a concrete subsequent discussion. I have therefore considered every candidate precursor, first of all, in terms of its robustness and of its error bar. Robustness is concerned with the amount of false alert that ought to be released if it relies on it. In other words, it is concerned with the number of events that occur and that are not followed by the expected seismic event. The error bar deals rather with the domain, in space and time, where the precursor is observed and that precedes a given earthquake. Indeed, this domain ought to be practically suited for societal needs.

Therefore, several seemingly promising and intriguing precursors, which at present are being investigated by authoritative Earth's scientists, could not be included in the present treatment, as at present there is still need to collect additional case histories, in order to estimate their respective robustness and error bars.

In particular, the reader ought to refer to several recent impressive attempts, which are reported in several issues of the present electronic journal. In this respect, the present paper is supposed to be hopefully followed by additional studies also by other authors, inspired by some similar criterion, aimed to set order in this discipline, which at present appears certainly excessively dispersive.

Summarizing, the result of the present paper appears to be almost a concise 'handbook' for the practical management of earthquake and volcano 'prediction'. This study, however, is to be considered only as a first working document, to be improved as soon as additional findings appear in the literature. At present, this discipline appears often confused, hence sometimes unduly debated. It is a moral obligation for Earth's scientists to set order in this vaguely defined topic. Some hard thinking is certainly required. An operative and conceptual order can be achieved only by applying a screening of methods and arguments, by means of subsequent step-by-step methodological and critical improvement.

In the present paper, the meaning of 'forecast' is first clarified, as it is the source of some basic - and very unfortunate - misunderstanding, mostly concerning communication between scientists, society, legislators, and decision makers.

In addition, the 'myth' has to be destroyed of the existence of any 'magic' phenomenon capable to 'forecast' earthquakes, because every event is a different case history and it must be considered independent of every other earthquake: any two events are never strictly comparable each other.

Giovanni Gregori

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