A study of the best-documented earthquake light events in North America and Europe by a group of researchers may finally shed light on the mystery of the earthquake lights.
Reports of eyewitnesses seeing strange bright lights in the sky minutes before, during or after an earthquake, were once dismissed as apocryphal, but a series of photographs taken during an earthquake in Nagano, Japan in 1965 proved that the phenomenon does exist. Acknowledging the existence of earthquake lights (EQL), however, posed new questions such as why they appear in the sky during an earthquake.
According to a new study published in the Jan.-Feb. issue of the Seismological Research Letters, the phenomenon is caused by a type of earthquake in which one of the Earth's tectonic plates is pulled apart, creating a rift. The tension creates an electronic charge which turns into light when it reaches the surface.
Robert Thériault , a geologist with the Quebec Ministry of Natural Resources, and his team analyzed 65 earthquake events with EQL reports from as early as 1600 AD to see what the events had in common. "We built a pretty large database of earthquakes with earthquake lights that happened around the world," Thériault said. "And eventually, when we started to look at them, we found a really striking pattern."
Majority of the documented earthquake lights were seen in quakes within a tectonic plate at sites of continental rifting, a category that comprises only five percent of all earthquakes.
"We don't know quite yet why more earthquake light events are related to rift environments than other types of faults," said Thériault, "but unlike other faults that may dip at a 30-35 degree angle, such as in subduction zones, subvertical faults characterize the rift environments in these cases."
The researchers also said that the earthquake lights could be more than just an intriguing phenomenon. They can also serve as a life saver since their presence can be an indication that the ground is about to start shaking, "If you see visible lights in the sky, and you live in an earthquake-prone area, they might be an early-warning sign that an earthquake is approaching," Thériault said.
