For the first time in front of a large earthquake detected foreshocks

Izmit earthquake took the lives of 17 thousand people.  (Photo dogaldonusum.)

A group of French and Turkish scientists led by Michel Bouchon of the University of Grenoble first got solid evidence to suggest that an earthquake can be predicted for a few minutes or hours before the crash.

If we believe the theoretical calculations, the crust becomes unstable in the hours prior to a major earthquake, but the discovery of this instability in the real world has been extremely difficult.

The researchers involved in the analysis of data obtained just before the devastating earthquake in Izmit, Turkey in 1999. On one of the seismograms experts noticed five small shocks in the last 20 minutes before the cataclysm, with a P-wave impulse every 2.4 seconds followed by S-wave. Due to the constantly identical difference between them can be assumed that they came from the same source.

Picking up data from other stations, the scientists were able to calculate the exact location of the epicenter. He was just a few hundred meters from the center Izmit earthquake. It turns out that it was due to these attacks.

Although five detected foreshocks (small earthquakes) differed in magnitude, on waveforms they showed a remarkable similarity. Mr. Bouchon and colleagues re having studied all their seismograms and counted a total of about forty such shocks, revealing a clear pattern: the attacks gradually became stronger, and their sources are closer, until the process is turned into a major hit.

According to the researchers, this discovery could indeed lead to the creation of an early warning. Specialists are going to look for similar patterns in other earthquakes seismograms.

Alas, even if their efforts are successful, the problem is resolved. Prevention and prediction — very different things. Evacuation to a few days, and warned available at best be only a few hours.

Furthermore, Ian Maine University of Edinburgh (UK) believes that such a system is not applicable to all areas of risk. For example, the San Andreas fault that passes through California — the most controlled in the world, but no one so far failed to detect foreshocks seismograms parkfildskogo earthquake of 2004.

On the other hand, the magnitude of the earthquake parkfildskogo was only six points, while the strength of Izmit to 7.6 points, so Mr. Bouchon believes that the preliminary tremors only makes sense to look at the analysis of the most powerful earthquakes.

The study is published in the journal Science.

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