Gravity signal can detect earthquakes at the speed of light

Two minutes after the world's largest tectonic plate shook off the coast of Japan, the country's meteorological agency issued its final warning to some 50 million residents: An earthquake has triggered a tsunami in edge. But it was not until a few hours after the waves hit that experts assessed the true size of the Tohoku earthquake of March 11, 2011.

And in fact, this quake has reached a magnitude of 9 - releasing 22 times more energy than experts predicted and causing at least 18,000 deaths.

Gravity wave: A case of gravitational waves on a planet, the oscillations alter the environment there. Gravity waves that we can see with the naked eye are waves in seas, lakes, tides, tsunamis, winds blowing over a mountain, waves on clouds. generated when the atmosphere or lake surface , the sea surface is disturbed.

However, until now scientists have found a way to estimate the size of earthquakes more accurately, faster, through the use of computer algorithms to determine the earthquakes. from steam waves at the speed of light.

"This is a whole new way to recognize magnitude earthquakes. If we implement the algorithm," said Richard Allen, a seismologist at the University of California, Berkeley, who was not involved in the study. With this calculation, we will have more bases to determine the magnitude of the earthquake, and push warnings to affected areas faster and more accurately."

Scientists typically detect earthquakes by monitoring ground vibrations, or seismic waves, with devices called seismometers. However, the warning signals they can provide depends on the distance between the earthquake and the seismometers. Meanwhile, warning networks in Japan, Mexico and California can only function well for relatively small earthquakes. And when earthquakes exceed 7 on the richter scale, earthquake waves can saturate seismometers. This makes the detection and warning of large earthquakes like Japan's Tohoku earthquake inaccurate.

The Tohoku earthquake that occurred in March 2011 was recorded as the largest earthquake in Japanese history. This was the earthquake that caused a huge tsunami that killed thousands of people and collapsed three nuclear reactors of the Fukushima Daiichi power plant.

Recently, researchers involved in the search for gravitational waves - ripples in space-time created by the motions of massive objects - have realized that those gravity signals, with the speed of light, can also be used to track earthquakes.

"The idea is that as soon as the mass moves anywhere, the gravitational field will go anywhere," said Bernard Whiting, a physicist at the University of Florida who worked on the Laser Interferometer's Gravitational Wave Observatory. changes and. everything can be felt. What's amazing is that the signal will be present even in the seismometer."

In 2016, Whiting and his colleagues reported that conventional seismometers could detect these gravity signals. Earthquakes lead to large changes in mass; those displacements create a gravitational effect that distorts both the existing gravitational field and the ground beneath the seismometer. By measuring the difference between these two systems, the scientists concluded that they could create a new type of earthquake early warning system.

"Gravitational signals show up on seismometers before the first seismic waves appear. By combining signals from dozens of seismometers, scientists can identify patterns to explain the size and location of major events," Whiting said.

At the present time, this model and method will not work for earthquakes of magnitude less than 8.3 magnitude. Because below this threshold, gravity waves are so weak compared to seismic waves that it is more difficult to detect.

Now, Andrea Licciardi, a postdoctoral researcher at the University of Côte d'Azur, and his colleagues have built a machine learning algorithm to do that pattern recognition. They trained the model on hundreds of thousands of simulated earthquakes before testing it on real data from the Tohoku earthquake. The model then accurately predicted the magnitude of the quake in about 50 seconds — much faster than other modern early warning systems.

The gravity signal is too weak to detect earthquakes smaller than 8.3 magnitude with current technology, and the system is not capable of providing much advance warning in earthquake areas already covered by earthquakes. seismometer. But it can provide more reliable size estimates of magnitude quakes, which is important, especially for predicting tsunamis, which often take another 10 or 15 minutes to produce. presently.

With this technique, seismologists in Japan can accurately determine the intensity of the most violent earthquakes like Tohoku and issue appropriate warnings.

However, at the present time, this model and algorithm have not been widely used. It is primarily set up for deployment in Japan - but only for earthquakes generated by a specific fault zone that are capable of producing "major earthquakes". In addition, this algorithm needs to be trained specifically for use in different regions because it is only in its first generation, and not yet compatible with other areas of demand.