Slight shifts in the magnetic field preceded the California earthquakes

Researchers studying medium- to large-scale earthquakes in California have discovered detectable changes in the local magnetic field that occur 2-3 days before an earthquake. In a study just published in Journal of Geophysical Research: Solid EarthWilliam Heavlin and his team found that the magnetic field change signal is weak but statistically significant, and the seismologists hope their technique can be refined to eventually help predict earthquakes.

“It’s a modest signal,” said Dan Schneider, director of QuakeFinder, an earthquake research division of Stellar Solutions, a systems engineering services company. “We’re not claiming that this signal exists before every earthquake,” said Schneider, a co-author of the study, “but it’s very intriguing.”

The idea that the magnetic field might shift before earthquakes has been around for some time, but has always been controversial. The US Geological Survey notes that “despite decades of work, there is no convincing evidence for electromagnetic precursors to earthquakes.”

Working with the Google Accelerated Science team, the scientists tapped into magnetic field data from a series of magnetometers at 125 sensor stations along major faults in California. They collected data from 2005 to 2019 when 19 earthquakes of magnitude 4.5 or greater occurred on the fault.

Their multistation analysis considered other types of processes that might affect the magnetometers but are unrelated to earthquakes, such as: B. commuter traffic. Distinguishing this type of noise from potentially earthquake-related signals is the biggest hurdle to interpreting this data, Schneider said. After training their algorithms on half the dataset, the researchers identified a signal that indicates changes in the magnetic field between 72 and 24 hours before the earthquakes.

Schneider said that in the future he plans to further refine the models to eliminate more ambient noise from the magnetometers. For example, in this study, considering the average influence of solar activity improved the results significantly. In further work, the team will use data from distant stations to further eliminate noise due to solar activity.

The work suggests that “there may be regular detectable changes in the magnetic field that, with further study and isolation, could actually support the construction of a prediction system in the future,” Schneider said.

Provided by Eos

This story is republished courtesy of Eos hosted by the American Geophysical Union. Read the original story here.