The Mystery of Earthquake Lights

For centuries, there have been reports of strange lights being observed before, during, and immediately after strong earthquakes. Here is the U.S. Geological Survey on “What are earthquake lights?”:

Phenomena such as sheet lightning, balls of light, streamers, and steady glows, reported in association with earthquakes are called earthquake lights (EQL). Geophysicists differ on the extent to which they think that individual reports of unusual lighting near the time and epicenter of an earthquake actually represent EQL: some doubt that any of the reports constitute solid evidence for EQL, whereas others think that at least some reports plausibly correspond to EQL. Physics-based hypotheses have been proposed to explain specific classes of EQL reports, such as those in the immediate vicinity of the causative fault at the time of a major earthquake. On the other hand, some reports of EQL have turned out to be associated with electricity arcing from the power lines shaking.

Until recently, photographic evidence of the phenomena has been ambiguous and of poor quality—resembling many purported UFO photos. But the proliferation of mobile phones with still camera and video capability has caused evidence to accumulate, and some scientists are now advancing theories of what may cause them, for example, “Prevalence of Earthquake Lights Associated with Rift Environments” (behind an academic journal paywall). Here is a poorly-titled National Geographic popular article on the phenomenon and research into causes, “Bizarre Earthquake Lights Finally Explained”.

Rare phenomena which occur at unpredictable times often take a long time to be confirmed, no less explained. Sprite lightning, for example, was first reported in 1730 and anecdotal reports from aircraft pilots flying in the vicinity of thunderstorm activity were numerous, but it was not until 1989 that unambiguous photographic evidence was obtained (accidentally) and the phenomenon acknowledged to be real.