Researchers studying medium and large earthquakes in California have detected detectable changes in the local magnetic field that occur 2-3 days before the earthquake. In a study now published in Journal of Geophysical Research: Solid EarthWilliam Heflin and his team found the magnetic field change signal to be weak but statistically significant, and seismologists hope their technique can be improved to eventually help predict earthquakes.
“It’s a modest signal,” said Dan Schneider, director of QuakeFinder, earthquake research at Stellar Solutions, a systems engineering services company. “We don’t claim that this signal is there before every earthquake, but it’s very interesting,” said Schneider, one of the study’s authors.
The idea that the magnetic field might change before earthquakes has been around for a while, but it has always been controversial. The USGS states that, “Despite decades of work, there is no convincing evidence for the electromagnetic precursors of earthquakes.”
In collaboration with the Google Accelerated Science team, the scientists made use of magnetic field data from an array of magnetometers at 125 sensor stations along major faults in California. They collected data from 2005 to 2019, in which 19 earthquakes with a magnitude of 4.5 or more occurred on the faults.
Their multi-station analysis took into account other types of processes that may affect magnetometers but are unrelated to earthquakes, such as rush hour traffic. Differentiate between this type of noise and potential EarthquakeSchneider said related signals are the longest barrier to interpreting this data. After training their algorithms on half of the data set, the researchers identified a signal indicating changes in the magnetic field between 72 and 24 hours before the earthquakes.
Schneider said that in the future he would like to refine the models to get rid of more ambient noise of magnetometers. In this study, for example, calculate the mean effect solar activity Significantly improved results. In the ongoing work, the team will use the remote station’s data to eliminate noise from solar activity.
The work suggests that “there may be systemic changes that can be detected in magnetic field that with further study and isolation, it could indeed support the construction of a prediction system in the future,” Schneider said.
William D. Heflin et al., Decades case-control study of California geomagnetometers reveals modest signal 24 to 72 hours before earthquakes, Journal of Geophysical Research: Solid Earth (2022). doi: 10.1029/2022JB024109
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