Japanese and Turkish researchers have found that electromagnetic waves can be detected before seismic waves from an earthquake, raising hopes that the phenomenon could alert experts more quickly to an oncoming temblor and help in disaster prevention.
The findings by a team of researchers on what they have dubbed the “seismic dynamo effect” were made by chance during studies of measurements taken during a disastrous earthquake in Izmit, Turkey, in 1999, one of the researchers said.
“Our detailed examination of the electric and magnetic data disclosed small signals appearing less than a second before the large signals associated with the seismic waves,” the team said in a paper.
Electromagnetic waves travel about 50,000 times faster than seismic waves.
Yoshimori Honkura, a professor of geomagnetism at the Tokyo Institute of Technology and a team member, said they will carry out further investigations and study its potential role in Japan’s quake-monitoring framework.
Honkura said he and his colleagues chanced upon the phenomenon after detecting electromagnetic waves near the epicenter of the magnitude 7.4 quake that hit northwestern Turkey in August 1999. At the time, they happened to be studying the strength and direction of electromagnetism near the epicenter.
Results of their data later showed that electromagnetic waves could be detected about 2.5 seconds after an earthquake that occurred at a depth of 15 km, some 0.7 second before the seismic waves reached the surface and caused the earth to shake.
According to Honkura, the electromagnetic wave itself is weak, but the team was able to observe the phenomenon because it happened in the early hours of the morning when artificial electric signals from places such as factories are few.
In an experiment last year, the team simulated a small-scale earthquake in Nagano Prefecture by using an explosive.
Basic research on the seismic dynamo effect is still necessary before it can be useful in warning of the occurrence of a quake, Honkura said.
Honkura said he intends to study more about the effect in places where there are fewer electric signals to obstruct such monitoring efforts, including in the Tohoku region.