When the next big earthquake hits somewhere in the world, it will arrive without warning, destroying infrastructure and putting lives in danger.
However, in the days leading up to the event, titanic geological forces will already be at work, warping the crust in subtle ways that could, in theory, predict the coming catastrophe.
One possible signal could involve flickers in the magnetic field that goes up and down around our planet. For decades, researchers have debated the merits of searching for magnetic signatures for impending tremors, for lack of convincing evidence.
A new case-control study conducted by earthquake finderA humanitarian research project within the systems engineering services company Stellar Solutions, in collaboration with the Google Accelerated Science team, concludes that there might be a good reason to continue the search.
Apply machine learning Using ground-based measurements of local magnetic changes in the lead-up to a series of significant earthquakes in California between 2005 and 2019, the researchers found signs of a pattern that warrants further study.
This is not to say that the effect they observed can necessarily be used to predict earthquakes, but it is a fascinating clue for future study.
“We’re not claiming that this signal exists before every earthquake,” said QuakeFinder director Dan Schneider. told Joshua Rapp Learn on Eos.
However, the findings could be enough to keep the controversial subject of electromagnetic forecasts of large tremors alive for a little while longer.
The premises behind the hypothetical fluctuations in the magnetic field before earthquakes sound reasonable enough. Some argue that the massive buildup of pressure in the crust before an earthquake could, in theory, change the properties of rock layers enough to influence their conductivity.
Other studies point to pockets of trapped gas accumulating before release creating the electrical currents necessary to affect magnetic activity.
Detecting the resulting ultralow-frequency changes in the magnetic field would give authorities a warning that something big is going to blow up, giving them time to prepare in the same way that communities might for a growing hurricane.
Unfortunately, what seems like a promising idea runs into a series of obstacles in its implementation.
For one thing, many things can create low-frequency oscillations in local patches of a magnetic field. Even increases in nearby traffic or small changes in solar activity can generate a hum that could be mistaken for a geological disturbance.
Unweaving a reliable signal from this noise requires having accurate measurement equipment at fixed locations near significant tremors. Even when that happens, it is necessary to record enough earthquakes of the correct size for a statistical sample.
With research sites located near fault lines throughout the state of California, Quakefinder is in a strong position to overcome these obstacles.
Buried magnetometers at the different research sites provided researchers with a considerable amount of data on earthquakes larger than magnitude 4.5.
After selecting earthquakes for which there were measurements from two nearby sites and excluding pairs of sites without adequate records, the researchers were left with measurements for 19 earthquakes.
This sample was then divided into two groups, one serving as the basis for a machine learning study that attempted to filter out potential patterns from known influences, and the second serving as a test for any potential discoveries.
The signal-to-noise ratio identified by the process and confirmed in the test was not exactly high. As the researchers admit in their published reportObvious electromagnetic anomalies before earthquakes “would have been observed, documented and accepted much sooner” in earlier research.
But they do suggest that something intriguing lurks in the electromagnetic glow like a suspicious scream in the storm, one that could be present up to three days before an earthquake strikes. Fine-tuning the researchers’ method using a larger sample could pinpoint what’s going on.
If future studies land on a reliable hum of impending doom in an area’s magnetic field, it may not yet be a universal tune, calling for even more testing at multiple sites around the world.
For now, the idea of using small changes in the planet’s magnetic field to forecast tremors remains controversial. But buoyed by results like these, further investigations could finally uncover the secret whispers of a breakpoint flaw.
This research was published in the Journal of Geophysical Research: Solid Earth.
