Scientists cannot yet accurately explain light flashes and lightning during earthquakes.
What was it - a strange light in the sky? Many people reported seeing strange lights in the sky during the night, a phenomenon that has been recorded for centuries before, during and after the earthquake, Stuff.co.nz writes.
Seismologists have disagreed about the causes of a hotly debated phenomenon called "earthquake fires" and sometimes lightning from earthquakes.
And, of course, it's not entirely clear whether the night lights in New Zealand were this phenomenon, or something else. One theory suggests that the resting electrical charges in rocks are caused by crustal stress and tectonics. The charges are transferred to the surface, where they appear as light.
Historical records tell of sightings of balls or orbs, brightly glowing lights, floating above the ground or in the sky.
Much like tidal events is considered an area that is notoriously difficult to explore. Tidal stresses and their impact on the Earth are weak, transient, but measurable, although many seismologists are not convinced by the theory of the "tidal effect" of earthquakes.
Earthquake light is also known to be difficult to observe, study, and measure. GNS seismologist Caroline Holden said there were sporadic reports of lights in the sky.
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“Unfortunately, we cannot measure these phenomena or their magnitude with our instruments to provide a clear explanation,” she said.
The phenomenon has been recorded for centuries. Some hypotheses suggest that the movement of rocks can generate an electric field, others that an earthquake can cause rocks to conduct electromagnetic energy, followed by the subsequent accumulation of electrical charges in the upper atmosphere.
Another theory suggests a connection between the electrical charge, or current, released by the ground and the buckling under the surface, as well as the magnetic properties of rocks.
The charge appears as light. People reported similar strange lights in the sky during the 2011 Christchurch earthquake. In 1888, before the great earthquake near the Hammer region, observers reported a strange glow in the sky.
One recent study collected documentary evidence of strange light sightings from 1600 to the 19th century. The study, published in the seismological journal Research Letters, writes that “As a result of an earthquake, a strong electrical charge is transferred from below the surface to the surface, or higher, depending on the conductivity of the rock, and appears as light.
“When such an intense state of charge reaches the surface of the Earth and crosses the earth - the air interface is expected to cause [electrical transmission and breakdown] of air and hence a burst of light emission.
"This process is believed to be responsible for the bursts of light emanating from the ground and expanding to significant heights as seismic waves from a large earthquake pass by."
The study says some seismologists also think the theory could explain other phenomena, such as changes in electric fields, strange fog, haze, clouds, humming during low frequency radiation or radio frequency transmission.
In the paper, the researchers write that light is more often associated with a type of earthquake in which tectonic plates jerkily interact with each other. Such earthquakes are also known as "rift" earthquakes, as they occur in the rift zone.