On September 7, a 7.1 magnitude earthquake struck central Mexico. The epicenter was located 11 km southeast of Acapulco, in Guerrero, one of the states with the most seismic activity in the country. According to a report from the Institute of Geophysics of the Autonomous University of Mexico, this region is located next to the boundary between the Cocos and North America tectonic plates on the Mexican Pacific coast. In this region, the Cocos plate is moving below the North American plate in a phenomenon known as subduction. The Mesoamerican trench is the geomorphological feature that defines the contact between these two tectonic plates.
During the earthquake, many people were able to see and record strange lights in the sky, similar to the northern lights, that flooded social networks a few hours after the earthquake. These are the so-called ‘earthquake lights’, a phenomenon that has been known since ancient times but for which there is still no conclusive explanation. In fact, the existence of these bluish-white flashes was questioned until the 1960s, when the first recordings of these events were produced during the earthquakes that shook Matsushiro (Japan). At that time, the seismic community accepted the existence of this unique phenomenon.
Proposed explanations
These are very rare events with very varied characteristics: light bands, spheres, zig-zag lines, light belts, rays, etc. However, and beyond other pseudoscientific theories, it is accepted that they are due to various geophysical processes that take place as a consequence of the earthquake and the enormous release of energy that occurs during it. Proposed mechanisms include piezoelectricity, frictional heating, exoelectron emissions, sonoluminescence, phosphine gas emissions, and fluid injection (electrokinetics). One of the most accepted explanations indicates that the friction of the seismic wave with certain types of rocks can cause electrical currents that are later expelled to the surface . As we have already said, the lights can be due to different causes: there is also the possibility that the electrical cables generate some of these lights weak and temporary lights.
According to the United States Geological Survey, earthquake lights are a phenomenon that could one day help forecast earthquakes in the few places where they occur.
