The mysterious "UFO lights" may occur at rifts, or nearly vertical faults as the crystalline structure of the magmatic stones, subjected to intense pressure, releases electrical energy, according to a study published Saturday in the journal Seismological Research Letters.

Mysterious "UFO lights", known as "ground lights" or "earthquake lights", sometimes appear before or during earthquakes and take a number of forms, including spheres of light orbs floating through air.

Some have confused the globular luminous air masses with UFOs. For instance, seconds before the 2009 L'Aquila, Italy, earthquake struck, pedestrians saw 10cm high flames of light flickering above the Francesco Crispi Avenue in the town's historical city center.

In 1988 a bright purple-pink globe of light moved through the sky along the St. Lawrence River near the city of Quebec, Canada, 11 days before a powerful quake.

Scientists said the "earthquake lights" are more likely to occur on or near a rift, an elongated depression in the Earth's crust bounded on both sides by normal faults.

Stress-activated mobile electronic charge carriers, termed positive holes, flow swiftly along stress gradients. Upon reaching the surface, they ionize air molecules and generate the observed light.

Continental rift environments now appear to be the common factor associated with earthquake.

Looking back at 65 of the recorded earthquake lights recorded in American and European documents dating from the 1600s, 85 percent appeared spatially on or near rifts, according to researchers.

"Earthquake lights as a pre-earthquake phenomenon, in combination with other types of parameters that vary prior to seismic activity, may one day help forecast the approach of a major quake," said Robert Thiriault, Geologist of the Ministry of Natural Resources in Quebec.