Earthquake warning system: only a few minutes

It is possible to approximate the intensity of an earthquake as soon as the vibrations begin, a new study suggests. This technology promises to help people get a few precious seconds to warn before the disaster really happens.

Predicting earthquakes is considered a difficult task. Scientists cannot point out when a fracture begins within a few days, months or even years before the event occurs. But the new method will provide a quick, accurate view of what will happen in just one minute.

" We can determine the magnitude of the earthquake in seconds before the first vibration and predict the movement of the ground from a few seconds to tens of seconds before it is felt ," Richard Allen, a seismologist at the University of Berkeley, California, said.

If such an automatic alert system is installed, children in schools will have enough time to crouch under the table and others have enough time to rush out the door, Allen speculated.

Models of P waves, S waves and surface waves. The forecast is based on the fact that a typical earthquake will broadcast three types of waves:

- Primary wave , or P wave , appears first. They move like a pressure wave, often creating a shock. Wave P has the least destruction .

- Appears after that a secondary wave , or S wave . It causes the ground to slide horizontally and vertically.

- Finally, surface waves , with the most destructive power . They shook the ground to the sides and then rolled up like a wave.

Allen and colleagues investigated the seismic wave record that occurred in 71 major earthquakes. They found that the frequency of the P wave is related to the intensity of the surface wave that appears last.

This argument contrasts completely with the conventional view - assuming that the intensity of an earthquake depends on a series of random events that lie along a fault, which occurs after the initial outburst.

New research results also " mean that the ultimate strength of a geological shake depends in part on what happens in the first few seconds ," Rachel Abercrombie, an earthquake specialist at Boston University, people independent of research and judgment.

" This kind of forecast is not a perfect system ," Allen said. But he also noted that all the strong earthquakes that the team studied to characterize the first few seconds had allowed for a useful forecast. " The magnitude of the earthquake predicted in the study differs only below 1 magnitude compared to reality ."

Another important factor for the prediction system is that not everyone is right on the spot where the earthquake occurs, and the shock wave propagates much more slowly than the signaling rate by the speed of the light wave. shining.

For example, if an earthquake occurs at the extreme north end of the San Andreas fault 1,280 km long, vibration will take 80 seconds (traveling at about 3.2 miles per second) to reach San Francisco. Of course, such an event does not destroy the City on the bay. But no matter where the earthquake center is, there will be a time to warn most of the last victims.

Allen said he had to test at least a year before a warning system could actually work. He envisioned using the Internet to transmit information about an earthquake. A computer on the other half of the world will translate this warning code to a specific location and predict the time and intensity of the imminent vibration. People can also call to inform.

T. An ( according to LiveScience )