Centuries-old reports of enigmatic "earthquake lights" have resurfaced, captured in videos preceding a recent 6.8-magnitude earthquake in Morocco. These captivating displays of vibrant, dancing lights have perplexed scientists for generations, with no consensus on their origins. However, experts unanimously affirm their existence.
John Derr, a retired geophysicist formerly with the US Geological Survey, who coauthored numerous scientific papers on earthquake lights (EQL), emphasizes that witnessing EQL relies on darkness and favorable conditions.
The recent video from Morocco bears resemblance to earthquake lights recorded on security cameras during the 2007 Pisco earthquake in Peru, according to Derr. Juan Antonio Lira Cacho, a physics professor in Peru, credits the proliferation of cell phone videos and security cameras for simplifying the study of EQL, a phenomenon once deemed unbelievable.
Earthquake lights manifest in diverse forms, as described in a chapter coauthored by Derr in the 2019 edition of the Encyclopedia of Solid Earth Geophysics. They may resemble regular lightning, luminous bands akin to polar auroras, floating spheres, or even small flames flickering along the ground.
To delve deeper into this enigma, Derr and colleagues analyzed 65 American and European earthquakes associated with reliable EQL reports dating back to 1600. Their findings, published in a 2014 paper in Seismological Research Letters, revealed that EQL occurred in roughly 80% of cases during earthquakes exceeding a magnitude of 5.0. These phenomena were frequently observed shortly before or during the seismic event, visible up to 600 kilometers (372.8 miles) from the epicenter.
Surprisingly, most EQL-linked earthquakes occurred within tectonic plates, not at their boundaries. Additionally, they were more likely to transpire near rift valleys—regions where Earth's crust had been stretched and pulled apart in the past.
Various theories attempt to explain the origins of earthquake lights. One theory, proposed by Freund, suggests that mechanical stress on certain defects or impurities within rock crystals generates electricity when rocks are stressed during tectonic buildup before or during major earthquakes. Rock, usually an insulator, transforms into a semiconductor when mechanically stressed, creating electrical charges that can flow through rocks at remarkable speeds.
While other theories, such as static electricity from rock fracturing and radon emanation, are also considered, there is currently no consensus among seismologists regarding the precise mechanism behind earthquake lights.
Freund envisions a future where the understanding of earthquake lights, and the electric charge they emit, could potentially aid in forecasting major earthquakes when combined with other factors. The mystery of these luminous outbursts continues to captivate scientists, driving them to unlock the secrets concealed within these captivating phenomena.