Found to occur in California. They occur 2 to 3 days before an earthquake. This relationship between the two was not known. It is now known that magnetic changes precede major earthquakes. The study is in the Journal of Geophysical Research: Solid Earth.
William Heavlin and his team found that the signal from the magnetic field change is weak but significant. Seismologists hope the technique can be used to predict earthquakes.
Cleaning up the noise
“It’s a modest signal,” Dan Schneider said in a statement. He researches earthquakes at Stellar Solutions, a systems engineering services firm. “We’re not claiming that this signal exists before every earthquake,” he said. “But it’s very intriguing.”
It was always a controversial idea. The U.S. Geological Survey says so. “There is no convincing evidence for electromagnetic precursors to earthquakes.” They took advantage of existing magnetic field data. They were taken from magnetometers at 125 sensor stations along major faults in California. They collected data from 2005 to 2019 There were 19 earthquakes of magnitude 4.5 or greater on the faults.
Their analysis took into account other types of processes that could affect magnetometers. It can happen even if they are unrelated to earthquakes, such as rush hour traffic. Differentiating this type of noise was the most complex, Schneider said. They trained their algorithms on half of the data set. Then they identified a signal that indicated changes in the magnetic field 72 to 24 hours before the earthquakes.
Schneider said that, in the future, he would like to further refine the models. He hopes to remove more environmental noise from the magnetometers. In this study, for example, taking into account the average influence of solar activity substantially improved the results. In continued work, the team will use data from remote stations. They will then be able to further eliminate noise due to solar activity.
The work suggests that “Knowing that these magnetic changes precede earthquakes would support the construction of a forecasting system in the future,” Schneider said.