During the 8.2 magnitude earthquake which shook Mexico, many citizens were witnesses of strange flashes of light in the night sky. Videos, photos, and comments flooded social networks, with people asking the source of the phenomenon.
In 2001, a NASA scientists, Friedemann Freund presented a study which claimed the lights were produced by the friction of tectonic plates, causing a positive charge in the earth's surface which then reacts with the free electrons in the ionosphere, causing the light flashes.
However, Carlos Mortera, a researcher at the Institute of Geophysics of the National Autonomous University (UNAM) said during an interview with EL UNVIERSAL, that the lights in the sky aren't related to the earthquake.
“Rain brings with it storms and lightning. It's very likely that at the time of the earthquake, it was raining and there were electrical storms,” he claimed, calling the whole event a “coincidence.”
Through his Twitter account, another user shared a video where it's possible to see several power transformers blowing up, causing flashes of lightning in the sky and power outages in the city. This could also be an explanation to the phenomenon witnessed.
VIDEO | En el Momento en que explotaban trasformadores durante el sismo costas de México de 8.4° Hay reportes de 5 Muertos. 65 Replicas pic.twitter.com/LfAehPaP8F
— Met Uy Estacion bcp (@Estacion_bcp) September 8, 2017
Mortera has also shared that there are several erroneous notions people usually believe in regarding earthquakes. For instance, he said it's no longer correct to talk about oscillatory or trepidatory movements. “This is just a way to explain the movements caused by quakes. There are seismic waves which may be lateral or horizontal, and surface waves which are of considerable magnitudes, like the ones felt in Mexico.”
Another mistake, according to Mortera, is to keep talking about the Richter scale. “This scale doesn't refer to magnitude, it refers to intensity, which is different. We use magnitude nowadays without adding the 'Richter', we just say magnitude.”
In order to measure magnitude, scientists have high-frequency seismograms, which allow to calculate magnitude, and based on that data, known the rupture of the rocks which caused the quake.
Mexico isn't the only country which has witnessed this phenomenon. Lights in the sky have also been seen in other earthquakes, such as the one in Chile in 2010; L'Aquila, Italy in 2009; Peru in 207 and recently in Ecuador, last year.