When the geological structure of the Earth changes, oscillations of the gravitational field arise, which propagate at the speed of light, much faster than seismic waves. The measurement of such oscillations can become a tool for predicting the effects of earthquakes, in particular tsunamis.
The journal Science published an article by seismologist Martin Vallée and his colleagues on the results of measuring gravity waves recorded after a devastating earthquake of magnitude 9, which occurred in 2011 in Japan. If the monitoring system relied on the data of gravitational oscillation detectors, then it would be possible to understand that the earthquake would be very powerful, a few seconds before it started. According to computer models, earthquakes of magnitude less than 8.5 do not give registered gravitational waves.
The data of gravity measurements are not taken into account by seismologists, therefore in 2011 it took 40 minutes for American observers to raise the rating from 7.9 to 8.8, and for Japanese observers it took three hours. Even a small increase in the magnitude of the earthquake means a lot of new destruction. And a few seconds of advance can save lives – especially in the case of underwater earthquakes, the most powerful of which lead to a tsunami.
Dealing with gravitational oscillations of geological origin, Valais and his team began to assess how such oscillations affect the operation of gravitational wave detectors, such as Virgo in Europe and LIGO in the United States. Gravitational waves, which are born of tectonic shifts, are much weaker than those that appear as a result of merges of black holes and neutron stars; For a long time, signals of the first type were considered too unreliable way to learn about earthquakes. But Vale and his team prove that at a distance of 1-2 thousand kilometers the difference in the speed of seismic and gravitational waves makes the latter a fairly reliable source of information.
Now scientists are looking for new evidence of their concept, in particular, data on gravity waves recorded during and after the earthquakes of 2004 in Sumatra (magnitude 9) and 2010 in Chile (magnitude 8).