Magnetometers have detected faint signals that can improve our understanding of what happens before earthquakes and offer promise for early detection.
Scientists in the middle of large earthquakes in California detectable changes in the local magnetic field that occur 2-3 days before the earthquake. A recent study found that the change in the magnetic field signal is faint but statistically significant, and seismologists hope that the technique can become a technique to eventually predict earthquakes. The research was recently published in the Journal of Geophysical Research: Solid Earth.
“It’s a modest sign,” said Dan Schneider, the study’s author. He is the director of QuakeFinder, an earthquake research company at Stellar Solutions, a systems engineering company. “We are not claiming that this signal exists before every earthquake, but it is very intriguing.”
Although always controversial, the idea is that the magnetic field can circulate for some time before an earthquake. The US Geological Survey (USGS) claims that “despite decades of work, there is no evidence of electromagnetic precursors to earthquakes.”
In collaboration with the Google Accelerated Science team, scientists recorded the magnetic field from an array of magnetometers at 125 sensor stations with major faults in California. They collected data from 2005 to 2019, during which time 19 earthquakes of magnitude 4.5 or greater occurred on faults.
Their multiplicity analysis estimated for other types of processes that can affect magnetometers but have nothing to do with earthquakes, such as rush hour traffic. According to Schneider, this kind of noise difference in the signals related to earthquakes is the biggest obstacle to interpreting these data. After installing their algorithms on half of the data, the researchers found a signal indicating changes in the magnetic field between 72 and 24 hours before the earthquake.
Schneider said that in the future, he wants to sharpen more models to eliminate more ambient noise from the magnetometer. In this study, for example, accounting for the influence of average solar activity substantially improves the results. As work continues, the team will use a remote data station to further remove noise due to solar activity.
The work suggests that “there are clear regular changes in the magnetic field that, with further study and isolation, could actually support the construction of a predictive system in the future,” Schneider said.
Report: “Case-Control Study on Decade of Ground-Based Magnetometers in California Reveals Modest Signal 24-72 hr Prior to Earthquake” by William D. Heavlin, Karl Kappler, Lusann Yang, Minjie Fan, Jason Hickey, James Lemon, Laura MacLean, Thomas Bleier, Patrick Leo and Daniel Schneider, September 1, 2022. Journal of Geophysical Research: Solid Earth.
Earthquake Interesting facts:
- The largest recorded earthquake in the world was a magnitude 9.5 (Mw) in Chile on May 22, 1960.
- The largest earthquake on record in the United States was a magnitude 9.2 that struck Prince William Sound, Alaska on Friday, March 28, 1964;
UTCCoordinated Universal Time or Coordinated Universal Time (UTC) is the primary time standard by which the world regulates clocks and time. Prior to 1972, this time was called Greenwich Mean Time (GMT) and was also known as "Z time" or * "Zulu Time" It is, within about 1 second, the mean solar time of 0° longitude.
- The world’s deadliest recorded earthquake occurred in 1556 in central China. It struck a region where most people lived in caves carved from soft rock. These dwellings collapsed during the earthquake, killing an estimated 830,000 people. In 1976 another deadly earthquake struck in Tangshan, China, where more than 250,000 people were killed.
- The earliest reported earthquake in California was felt in 1769 by the exploring expedition of Gaspar de Portola while the group was camping about 30 miles southeast of Los Angeles.
- It is estimated that there are 500,000 detectable earthquakes in the world each year. 100,000 of those can be felt, and 100 of them cause damage.
- Each year the southern California area has about 10,000 earthquakes. Most of them are so small that they are not felt. Only several hundred are greater than magnitude 3.0, and only about 15-20 are greater than magnitude 4.0. If there is a large earthquake, however, the aftershock sequence will produce many more earthquakes of all magnitudes for many months.
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