Some earthquakes ‘are preceded by magnetic field changes’ days beforehand
Earthquakes in the US state of California are preceded by changes in the local magnetic field in the days before a quake hits, researchers have found.
The changes are detectable and could one day help to forecast devastating earthquakes, the researchers hope.
"It's a modest signal," said Dan Schneider, director of QuakeFinder, an earthquake research department in Stellar Solutions, a systems engineering services company.
"We are not claiming that this signal exists before every earthquake, but it is very intriguing."
The idea that the magnetic field may shift before earthquakes is not new - but it’s always been controversial.
The US Geological Survey has written that “despite decades of work, there is no convincing evidence of electromagnetic precursors to earthquakes”.
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Schneider said that the research suggests “there may be regular detectable changes in the magnetic field that with further study and isolation, could actually support the construction of a forecasting system in the future".
In collaboration with the Google Accelerated Science team, the scientists tapped into magnetic field data from an array of magnetometers at 125 sensor stations along major faults in California.
They gathered data from 2005 to 2019, during which time 19 earthquakes of magnitude 4.5 or greater occurred on the faults.
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Their analysis accounted for other kinds of processes that might affect the magnetometers but have nothing to do with earthquakes, such as rush hour traffic.
Differentiating this kind of noise from potential earthquake-related signals is the tallest barrier to interpret these data, Schneider said.
After training their algorithms on half 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’d like to further hone the models to eliminate more ambient noise from the magnetometers.
In this study, for example, accounting for the average influence of solar activity substantially improved the results. In continuing work, the team will use remote station data to further eliminate noise due to solar activity.
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