Despite centuries of reports of anomalous luminous phenomena (ANP) – lights, glows, flames, sparks and clouds – before, during or after an earthquake, the scientific view of such reports remains deeply divided. The evidence for earthquake lights (EQLs) and associated anomalies consists overwhelmingly of anecdotal accounts. But scientific evidence has been accumulating, and in the past 10 years a plausible theory to explain the host of unusual precursors has been proposed. Geological reference sources fail to address the wide breadth of ideas within this topic, and mystery-themed sources contain mostly non-scholarly information that is dubious or exaggerated. A balanced view was needed. So, here is the Spooky Geology examination of the credibility and cause of earthquake lights and associated ANP.
Quebec, Canada, 25 November 1988, 18:46 local time.
It was dark when Joseph Dallaire, a trapper in Laterriere, was leaving the conifer forest after checking the traps near his home. The weather was mostly clear and cold with a low wind. After exiting the woods, he headed to his house across the open field 700 meters away when he was startled by a crackling sound approaching from behind. This sound was followed by a 6-15 m high curtain of bluish light that passed by him in about 2 seconds. Then he felt the shaking from the magnitude 6.5 earthquake which had occurred in Saguenay 19 km away. Dallaire described the light to a researcher as hugging the ground as it moved past him, passing into the open field, and disappearing to the northwest. He reported that the light was bright enough to illuminate his house. It was not like normal lightning but the crackling sound suggested an electric field buildup and discharge off the tree branches. The curtain or sheet of light suggests a strong electric field from the ground that resulted in a discharge at the ground-to-air interface. The discharge was traveling away from the direction of the Saguenay quake epicenter. 
What can we make of this remarkable event? It was not the only luminous phenomenon noted in association with this unusual quake that took place within the continental land mass, far from a plate boundary. At 29 km depth, it produced strong shaking but few aftershocks indicating a distinct release of energy. The Saguenay earthquake lights were relatively well-studied  yet we still have a mystery regarding the Dallaire experience.
The topic of earthquake lights is both highly technical and popular with lay audiences, making it difficult to discuss in popular discourse. This is not a unique problem as it occurs in most scientific fields. With most Spooky Geology subjects, there exists a popular idea about the phenomena but the detailed scientific ideas are buried within the specialized literature of various subjects. For EQLs, we can find snippets and threads of the discussion in natural history, geology, geophysics, rock mechanics, and seismology, but also in folklore, psychology, and cultural studies. What typically is supplied to the public from mainstream news and entertainment sources is nontechnical, unchecked, and often exaggerated or wrong.
Scientific journals and reliable media reports hold a wealth of observations and reports of EQLs. Often thought of as folklore, there are many highly technical explanations suggested by qualified experts, not cranks or wacky amateurs. Those interested in strange phenomena likely are not aware of the current state of thinking on the topic so let’s assess the big questions: Is there something here to explain? And what are some reasonable means to explain it? What does the scientific community think in comparison to the public? Could mainstream seismology be missing something or are EQLs all misperceptions or misinterpretations of other things?
Lights originating from the earth (not the sky) have been reported for millennia.  “Earth lights” is a term that encompasses several reported but still questionable phenomena frequently associated with paranormal and fringe ideas. Many places are noted for recurring observations of slow-moving or stationary balls of light with no apparent source – Hessdalen valley in Norway and Brown Mountain Lights in North Carolina. These phenomena have been related to seismic stresses or geochemical processes that generate electric fields. Mysterious balls of light called “spook lights” or “ghost lights” are known from many locations. While these may be at least partially explained by atmospheric conditions that produce refraction of man-made lights from cars, trains, or planes, some have been reported long before modern transportation. Ball lightning, while related to storm events, seems to come from a ground interaction with typical lightning and is reported by witnesses to behave very strangely. Both ball lightning and spook lights are sometimes described as acting “intelligent” – moving away as people get closer or following cars. Earth lights as genuine natural phenomena are controversial for reasons I’ll explain further on. Reports of near-earth lights obviously cross over with descriptions of UFOs. The Condon Report, the US government’s final word on UFOs in 1969, explained some reported UFOs as natural luminous phenomena – that is, it invoked a mystery to attempt to explain another mystery. 
Lights in association with seismic activity were reported before today’s modern electrified cities existed. They are also reported over the ocean or as luminous balls in the water. Galli, an Italian priest, published 148 observations recorded from 89 BC to 1910 in Europe.  Montandon developed a system in 1948 to categorize lights . Types of ANP include the following:
- Flashes or sheet lightning that illuminates the sky
- Slow-moving globes or floating balls of light
- Bands or rays in the sky, or columns emanating from the ground
- Small or tall flames from the ground that shimmer
- Diffuse glows usually over mountains.
But that’s not all, as the Daillaire event showed. Sparks and electricity crackling on high points have been noted, sometimes related to radio interference as happens during lightning strikes during a rainstorm. [2, 4, 6]
EQLs of these various types have been reported before, during, or shortly after the shaking, mostly related to quakes above magnitude 5. They are witnessed seconds or weeks prior and last seconds to minutes in duration. One researcher estimate they may occur only in association with 5-6% of all quakes. So they are not common. 
In 1968, a swarm of quakes occurred that were pivotal to the history of EQLs called the Matsushiro events. Mr. Kuribayashi, a dentist, took a series of photos in succession, showing a sustained hemispherical glow over Mt. Kimyo in Japan, lasting about 90 seconds, and then the glow diminished. Other glows associated with the same event lasted from 10 seconds to 2 minutes. John Derr of the US geological survey was a proponent of EQL in the 70s. He considered these photographs, brought to the public by Yasui (of the Kakioka magnetic observatory in Ibaraki) as the best evidence for EQL we had so far. Yasui also noted what’s called “sferics” – radio interference in 10-20 kHz range – associated with some earthquakes. 
On July 1, in either 1972 or 1973 (for an explanation of this discrepancy, see [5 – electronic supplement]) visitor Jim Conacher photographed seven luminous globes on Lime mountain near Taglish Lake, Yukon, Canada. He thought he was seeing UFOs. These slow-moving orbs, also called “slow meteors”, are typical of globular EQLs that travel in curious paths, not like a solid object exhibiting ballistic motion. The Cross Sound earthquake M=6.7 occurred on the suspected date of the photo. The orbs reportedly drifted upwards and there were no known causes for lights to appear there. 
The following dramatic and spooky photo depicts a flame-like version of EQLs. Not widely circulated, this spectral photo from Brasov, Romania is said to have been taken 100 km from a M= 7.4 epicenter quake in the Vrancea Mtns in 1977. Damage and loss of life occurred in Bucharest resulting from vertical slip of a thrust fault. [5 – elec. supplement]. Edit: According to Derr (personal communication), this photo may be a result of a camera malfunction).
Old Chinese folklore tales tell of clouds that looked like dragons appearing in the sky as a signal of a coming quake. Iridescent clouds are featured in a video taken about 30 minutes before the Sichuan/Wenchuan quake of May 12, 2008. The rainbow effect of these clouds is the result of small ice crystals or water droplets acting like a prism, diffracting or scattering light.
Skeptics argue that these clouds are neither earthquake lights nor particularly anomalous and are not related to the quake at all. But the observers found it to be remarkable enough to film it, so it was unusual. Ground-based electromagnetic seismic precursor observations have been employed in China for 40 years. For this 2008 quake, equipment recorded different anomalies near the epicenter of this quake from those of the outlying areas 300 km away. Researchers speculated that the difference could be explained by the different stress regimes – compressional vs extensional as the fault stressed a large area of crust. The electromagnetic emissions were three orders of magnitude higher than normal background. Ionosondes in the upper atmosphere recorded a giant positive (charge) disturbance in the ionosphere on May 9, three days before the quake. 
Other anomalous phenomena
Besides lights, there are other phenomena associated with earthquake precursors. As with lights, they are diverse with none being systematic or reliable in occurrence.
During the preparation time for a quake, rocks dilate and compress, opening and closing the tiny spaces within the rock. The opening, then squeezing, affects the water and gas in the rock spaces. We, therefore, see changes in the levels of groundwater and radon gas released in response to seismic events. Groundwater changes in wells and springs are commonly reported. This is not controversial. Even as the energy from a strong quake passes around the world, scientists recorded a small but significant effect on groundwater levels. Nearer to the fault, there may be extraordinary changes including temporary artesian effects, the appearance of new springs, or permanent changes in groundwater flow patterns. [8, 9]
Gas release (into air or water) is also not disputed. Radon release can be measured locally several times above the average concentration in the lead-up time to a large quake. Radon is radioactive and ionized the air, but not enough to generate electric currents to explain EQLs.  In Kobe, Japan, 1995, radon increased for several months before the main shock, peaking nine days prior at 10x normal concentrations. Radon emissions as earthquake precursors are a focus for Japanese researchers [11, 12] and were highly controversial in the L’Aquila, Italy event in 2009.
Several incidences of radio frequency pulses and anomalies, in the ULF and ELF ranges, have been recorded and later connected to a seismic event. In Loma Prieta, CA, 1989, magnetometers put in place by Stanford University for another purpose recorded a 20x increase in ULF energy 14 days prior to the main shock. [13, 14, 17] In Chile, 1960, an unusual radio event occurred 5 days prior to a large quake. It was recorded via four receivers monitoring solar activity. At the time, the cause was a mystery and the subject of a paper in 1963. Much later, that same researcher correlated the anomaly to the quake and wrote an update in 1982.  Unfortunately, this network never again caught a similar event. When very low-frequency anomalies were detected on the San Andreas fault in the 80s, scientists thought this type of monitoring looked promising for prediction. Further studies into the predictive nature of these signals were not so promising and interest waned. 
Related to the radio frequency anomalies is the concept of ionospheric coupling. Sergey Pulinets in Russia developed the idea of seismo-ionospheric coupling in the 1990s.  He explored the connection between earthquakes over magnitude 5 that sometimes were preceded by anomalies in the ionosphere. The ionosphere is the part of Earth’s upper atmosphere from about 60 to 1,000 km altitude that is ionized by solar and cosmic rays, but reflects radio waves. Russian and Chinese scientists are actively working on gaining more data on this using remote sensing via satellites. Some experiments measuring the ionosphere found a change in total electron content in the general area over the preparation region of a quake. [10, 12, 15, 18] The anomalies, noted a day, to weeks, to months ahead, are suspected to result from a stream of positive charges released from the ground surface in relation to increased stress from the fault, thus changing the electrodynamic properties of the atmosphere. Though it sounds obvious to look for anomalies such as these, it is difficult to pinpoint them because of regular fluctuations in the ionosphere from solar events and other normal causes of disturbance. Not all faults would even produce this signal (especially those underwater). 
Surface thermal anomalies have also been spotted via satellite some 100-500 km across a few days before major events.  An example included a 2001 quake in Bhuj, India (magnitude 7.9) where infrared emission was spotted several days before.  Thermal anomalies fluctuate and disappear and can cause an increase in apparent ground temps. That is, people on the ground report feeling a rise in air temperature but it is not reflected in the recorded local ground temp. [6, 7, 10, 11]
Several other atmospheric anomalies are associated with anecdotal reports prior to earthquakes including fog and strange clouds. Pliny the Elder and Aristotle considered strange clouds as EQ precursors and the belief is still held and reinforced by the “rainbow cloud” reports.  The idea of “earthquake weather” is a weak claim. Some local folklore claims the weather gets humid or rainy before a quake, which is consistent with the idea of electrical charge release that ionizes the air and can cause aerosols or nucleation of water vapor and rain. Rain before quakes has led to a mistaken belief that rain “lubricates” a fault. It doesn’t. But some have a local belief that hot and dry weather is indicative of a coming quake. That appears to be a myth since there is no correlation. If there is little moisture in the air but electrically charged particles are flowing out of the ground, then sparks or coronal discharges could be possible from pointed or irregularly shaped objects (also known as St. Elmo’s fire). Recall that a crackling sound preceded Dallaire’s view of the light curtain that came from the trees…
Biological anomalies are legendary when it comes to earthquake prediction. [20, 28] There are myriad tales of animals behaving strangely for days, weeks, or, most often, seconds before shaking is felt. Separate mechanisms are likely involved as animals can certainly detect tiny shaking, low-frequency vibrations or minute signals of the shaking seconds sooner than people. It’s the longer lead time reports that are curious and historically examined as a basis for warning systems. There are some lab data on this but it’s not robust . The idea persists because of post hoc anecdotes. Animal reports from the affected areas are problematic due to the lack of controls for the observations. They are also unreliable due to suggestion and memory contamination because they are described after a stressful event. However, fish and small mammals are sensitive to electrical signals, so if a mechanism is found that produces such signals, it’s reasonable to attribute some anomalous animal behavior to this condition.
There are even reports of plants and trees looking unusual prior to a quake and of people feeling uneasy or ill.  From the few studies that exist, there is just not a decent body of evidence to go on.
Other spooky things have been reported in homes. Magnets temporarily seem to “demagnetize” hours before a quake. Radio and TV static is noted, and electronic devices and appliances malfunction.  Magnetic field anomalies have been recorded in conjunction with a quake. For the Loma Prieta, California event in 1989, an elevated signal was recorded through a network of devices two weeks prior and a very high signal three hours before. [13, 33] But the instrumentation lost power during the quake itself so there could be no follow-through to check what happened post-quake.
Many of the notable historical reports of lights and other anomalies pre-quake occur in continental areas not near subduction zones in areas where there is a type of extensional faulted area called a “graben”.  The earliest reports are vague with later reports being less so but still uncertain in detail.
New Madrid, Mississippi, 1811
This historic quake took place on the Mississippi River graben in an area of America sparsely populated at the time. An incredible 40,000 square miles of land was affected by the estimated ~7.9 magnitude quake. Luminous phenomena appeared in the epicentral area including sparks from the earth, exploding flashes and sheet lightning in the sky, but up to 600 km away, people also saw flashes and a glowing sky like “fires in the air”. [5 – electronic suppl., 21] See Spooky Events from the New Madrid Quake.
Lisbon, Portugal, 1755
8 days prior to this tremendous quake, worms appeared all over the ground. Other unusual animal behaviors, strange lightning and flames from the mountainside were also observed. 
Sonora, Mexico, 1887
The 7.2 magnitude quake was very strong for this area and fault movement extended into Arizona. People thought volcanoes were erupting as they observed blazing craters in the mountains. Scientists discovered scorched trees over the fault line. 
Idu peninsula, Japan, 1930
1500 reports of luminous phenomena were associated with this quake that occurred at 4:30 am. Carefully recorded eyewitness reports included descriptions of the sky lit up by fireballs and beams and columns of light. A series of round lights in a straight line were seen moving through the sky. 
Haicheng, China, 1975
This was a most remarkable event that began in December of 1974 when unusual animal behavior was noted by trained observers. Snakes came out of hibernation and froze on the ground, rats acted confused, chickens and cattle were excitable. In addition, the groundwater table changed, artesian wells appeared, springs became cloudy, and gas bubbles appeared in ponds. Many small quakes occurred but by February, reports of anomalies climbed steeply in number. Ground fog was noted as near-surface humidity increased. On February 4, an evacuation of the town was ordered. Then, at 7:36 pm a 7.3 magnitude quake occurred. The evacuation was credited with saving thousands of lives saved. [23, 20]
Tangshan, China, 1976
Fireballs and flashes were seen 200 miles away from the area where the next night a 7.8 magnitude occurred. 240,000 people were killed (or more). Changes to ground resistivity changes were recorded and there were some reports of fish acting strangely. 
Saguenay, Quebec, Canada, 1988
46 good reports of luminous phenomena were collected during this swarm of 67 quakes: light balls floating a meter off the ground, motionless “meteors” (some with streamers) popping out of the ground, rays and bands across the sky. The main shock of 5.9 magnitude produced the Dallaire account of a crackling light curtain. Observation of the lights was found to be correlated to location of grabens. [2,7]
Kobe, Japan, 1995
Seconds before the magnitude 7.2 quake, blue-white streaks were observed from the fault area. The longest lasted more than 30 seconds. White luminous hemispheres 100-200m wide appeared near the ground and floated upwards. Flashes appeared at the same time as the shaking, even on the little-industrialized island of Awaji. At the surface exposure of the fault, plant roots were found scorched, the minerals had been locally heated high enough to melt silicates in the rock. [25, 26]
There are many other similar events associated with anomalies in the historic literature including several reports from sailors who described glowing balls that rise from the ocean depths and burst on the surface and discs of lighted water. Speculation as to the cause of these anomalies include the electrolysis of seawater or response to environmental stimuli by self-luminescent animals. 
Modern strong quakes get significant media attention. Events are recorded via security cameras and mobile phones and distributed on social media. Recording of lights, strange clouds, glows, and flashes are the subject of YouTube and Facebook videos prompting interest in the idea of EQLs.
Fidani  published a study of observations from L’Aquila Italy in 2010. After several foreshocks, a magnitude 6.3 event occurred in April 2009. Eyewitness interviews resulted in collection of 241 reports of luminous phenomena but 1057 anomalies in total. Locals reported flames emanating from the ground after the main shock 10 m high and small flickers from poles and between the cobblestones just prior to the main shock. The sky glowed red or orange before the quake, with violet clouds and fog, especially over the mountains. Sparks came off rough or pointed surfaces. 71 flashes were cataloged before and during the main shock from a clear sky. Fireballs, glows, and streamers similar to an aurora appeared above. Radio phenomena and unusual sounds were also noted. 305 biological observations were logged including that of a biologist who noted that the toads she was studying disappeared. after several foreshocks.  Giampaolo Giuliani was an amateur researcher making radon measurements. He made an unofficial prediction based on his measurements but he was cited by government officials for making dangerous public pronouncements and silenced.
Carlo Strinella, a resident near L’Aquila, already heard of EQLs. When he saw flashes, he took his family out of the house. Here is an account taken from Fidani:
“At about 01:30 on 6 April, just two hours before the main shock, Carlo Strinella saw two white light flashes reflected on the furniture of the kitchen, whose shutter was open. The second flash was intense as daylight, lasted more than 1 s, and was left impressed on his retinas. He checked that everything was fine in the kitchen, and looked out the window but saw the stars, and did not hear thunder. Then, he remembered having read an EQL summary a few months earlier and decided to take his family to a safer structure. He also noticed that the air temperature outside had sensibly warmed up during the night in comparison with the feeling he had immediately after dinner time, at about 21:00.” 
L’Aquila reports of anomalies span a wide spectrum. But the Fidani survey was done after the event when the researcher declared one of his aims was to instruct the public about EQLs, so we must be careful about taking these anecdotes at face value. Other than the glowing skies, I can find no other physical evidence recorded. Radon, EM frequencies, groundwater levels and infrared anomalies are measurable. If changes in these parameters did occur, anomalies could be recorded.
Three recent events have increased public interest in EQLs.
Lima, Peru, 2007
Security cameras caught light flashes as the shear waves passed from a magnitude 8 quake. A Navy officer reported blue columns of light bursting four times in succession from rocky outcrops in shallow water between his ship and the shore. 
Kaikoura, New Zealand, 2016
This 7.8M event occurred at night. Several people recorded green and blue flashes in the sky. These were said to be over the sea but that is not clear.
Mexico City, Mexico, 2017
Several light flashes in the distance were recorded from surveillance cameras.
Acapulco, Mexico, 2021
Like the Mexico City quake of 2017, people caught on camera flashes in the sky minutes after the quake. This is significant because electrical transformers and wiring were clearly disrupted, and the sky was cloudy to reflect the light. In addition, there were apparently thunderstorms in the area. This event created a flurry of interest in EQL based on a misunderstanding: people assumed the flashes were either a result of the fault break or that all flashes, regardless of cause, should be referred to as EQLs.
All four of these events were called “EQLs” but they are questionable. The flashes look conspicuously like electricity transformers exploding or arcing as electrical wires touch. This produces very bright white-blue light that can be reflected by clouds. (Perhaps even the Matsushiro photo could be an electric transformer.) It’s more plausible that this is the explanation for these lights because we know this happens during large quakes in urban areas.
Frustratingly, we have not seen recorded the more unusual forms of EQLs like ground flames, fireballs, sparks and columns. Light pollution, large swaths of paved areas, and lack of connection with the natural state of the land may mean that subtle natural anomalies are masked or that we don’t notice environmental changes as we did in the past.
The scientific/seismological view of EQLs remains one of skepticism, for good reason. Science is inherently conservative in changing to a new paradigm. Enough trustworthy evidence must be accumulated for the shift to occur and often various social factors make it happen even more slowly. Most of the evidence for EQLs is anecdotal – the worst kind of scientific evidence. Anecdotes can lead you where to look but they contain noise and errors. How would scientists credibly record these observations? Earthquakes happen all over the world and in indeterminate time frames. To set up observations for EQLs and associated precursors, the scale and scope are huge.  There are multiple variables that need to be measured and coverage in time and space must be adequate.  Even in the situation of known seismically active areas, this is often prohibitively expensive. Not all faults will produce precursors as subsurface regimes are different, even from one quake to another. Perhaps atmospheric conditions could have an effect on perceiving precursors. Since they clearly are not reliable to the extent that we can readily distinguish them, we can conclude they are more of an exception rather than usual. The lack of a plausible mechanism inhibits research. If we don’t have some idea how they COULD be, it is more difficult to plan to catch them.
Finally, scientists are skeptical because not much progress has been made due to the above problems. EQLs fall into the realm of legend and myth and have been lumped into paranormal subject areas like UFOs, ghost lights, and poltergeist activity. Many claims of EQLs seem to be explainable by other causes such as post hoc claims being inaccurate due to stress or misinterpretation, asserting undue meaning to non-associated events (such as iridescent clouds and animal behavior), and alternative coincidental causes such as electrical arcs or regular fires as a result of quakes.
Traditional research in seismology has been focused on mechanical observations – ground deformation, and prior events.  Because the reported precursors are very diverse, it’s hard to fathom whether they have the same mechanism. Besides that, we don’t know what the mechanism could be.
The “father of seismology” Robert Mallet talked about EQLs back in the 1850s in his volumes On the Facts of Earthquake Phenomenon.  In 1931, 1500 reports existed, collected by professional researchers. Some said at that time there was no doubt they exist.  Again in 1973, John Derr of the USGS called them “well established” based on the many documented reports.  Several scientists publishing on these topics repeatedly state that EQLs are accepted to exist. This is curious because they remain notably controversial in the bigger geological framing.
“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.”
Various mechanisms have been proposed to explain EQLs. But, how does the charge get to the surface? If we confirm the occurrence of the charge at the surface, then there is a basis for the reports and they will be greater acceptance. A mechanism that produces air ionization, where electrically charged particles also act as nuclei for condensation and release latent heat, could be at play. Air ionization could possibly produce coronal discharges, sparks, plasma emissions, effects on animals, fog and clouds, and electromagnetic anomalies. The mechanism derived from fault stress must be able to concentrate and maintain large charge densities to reach the surface and release it. Charge accumulation and movement are a problem.  Plate tectonics results in squeezing, grinding, and breaking rock slabs and mineral grains on a huge scale. It would be surprising if you don’t get something electrical going on. Several mechanisms to account for EQL and associated phenomena have been proposed:
- Streaming potential. Fluids forced through small pathways generate electrical charges. This does not seem to produce high enough voltage. 
- Piezoelectricity.  Some minerals like quartz which is abundant produce an electric charge when pressure is applied. This is a favored idea regarding EQLs, however, this happens in a short span and decays quickly as the + and – charges cancel out due to random distribution of crystals.  Though it can be associated with radio frequency emission, there seems no way to concentrate the charges and them get them to the surface.
- Vaporization in shear zone. High stresses in the fault zone can produce charge separation and dramatically increase conductivity. Once again, this only works if the path to the surface is short where it may produce a coronal discharge above the fault. Several variables are also at play: amount of water available, width of shear zone, sliding velocity, the breakage of rock (as in a new fault), and the level of stress buildup. 
- Sono luminescence.  An intense sound wave can cause gas bubbles in liquid to collapse producing a burst of light. What if the same happens with an intense seismic wave? This idea didn’t go very far as it does not account for reports of light beforehand and the effect must occur close to the surface.
All these processes may be going on but none seem to be able to produce what is observed as EQLs on a large scale.
Peroxy defect theory
The current leading candidate for a mechanism is that of the peroxy defect theory. Friedemann Freund is the discoverer and primary promoter of this unifying theory – combining ideas from semi-conductor physics, chemistry, and rock physics into this framework to explain the generation, concentration and movement of a charge cloud to the surface. In simplified terms, the idea is this: There is a percentage of “peroxy defects” in the minerals that make up igneous and metamorphic rocks. The defects in the molecular structure occur when the oxygen molecules are not in their typical valence state but connected by a weak oxygen-oxygen single bond. Under stress, these bonds break and release positive charge carriers, called positive holes (P-holes), which flow via grain-to-grain contact in the rock. They move fast (200 m/s) and far (several km). The cloud of charged particles moves from high to low stress and upon reaching the surface, the theory goes, the cloud can generate local electrical fields that produce massive air ionization causing coronal discharges or bursts of light. Freund concludes this is what generates the necessary charge for the observed EQL effects and associated phenomena. He has demonstrated the charge concentration and movement in the lab on a small scale by stressing rocks. He reports that at around 2 seconds before the rock slab fails, a burst of positive ions is released from the surface of lower stress. The stress gradient drives the movement of the charge. The flow is away from the fault and, notably, to high points like mountains or asperities (areas of rough surface or points). Pointed and irregular structures produce a higher potential gradient and are more prone to emit the corona discharge. Peroxys are not very controversial but this idea to explain EQLs and precursors has not received much attention from seismologists (who are mostly trained in geophysics, not solid-state physics or chemistry). [1,5,10,11]
The peroxy defect theory has its problems – an obvious one being how to test it. We can’t assume that lab results of stressed rock slabs are equivalent to underground conditions. Real-world conditions may be far more heterogeneous and not conform to the ideal conditions that would allow the formation of currents. Freund notes that charge flow may be focused in some areas and blocked in others due to the heterogeneity of the crust. If valid, however, this theory could account for lights of various kinds, fog, clouds, thermal infrared anomalies, ionospheric perturbations, animal behavior, and even strange everyday anomalies because of the cloud of electrically charged particles leaving the ground surface en masse. Perhaps the passing of shear waves may also produce forces that activate the peroxy defects, which may explain Dallaire’s event.
But it’s still just proposed. Dr. Freund and colleagues are having a difficult time getting a forum with today’s seismologists who, generally, still do not consider EQLs and other precursor reports to be important or meaningful. Scientific data gathered so far in support of EQ anomalies was often lucky observations or anecdotes. There are no statistically meaningful data sets yet. Even though some may recognize widely reported anomalous precursors as an unsolved problem, these observations don’t yet fit into the picture, therefore, mainstream seismology efforts are not geared toward supporting an investigation into it. The non-interest in precursor research may be associated with the geological conditions of the U.S. Earthquake precursors such as EQLs are not as prevalent in the U.S. – 90% of such reports are in rift areas in other parts of the world (though several oddities have been reported in modern times in California including Monterey Bay, Hollister, and Santa Rosa). [5 – elec. supplement] Most papers published on anomalous precursors are not in English but are from China, India, Russia, Taiwan and Japan. And finally, the idea of EQLs is tainted by its association with spooky things.
The tectonic strain theory is popular with paranormalists who wish to explain ghosts and hauntings by a localized, natural mechanism.  Michael Persinger is a neuroscientist who proposed that fault areas produce stress-induced, transient geophysical fields. Even when no quake occurs, these fields may affect the temporal lobe of the brain which could explain why people report lights and bad feelings, possibly have hallucinations, and experience strange electrical malfunctions making a house appear “haunted”. The data is not robust and additional investigation into the TST petered out.
Strange lights before catastrophes have a folkloric connotation of being “fire from heaven,” “the opening of Hell,” and are associated with superstition and bad omens. During a stressful time, people report weird events and exaggerate or get confused about what they saw which is why anecdotes surrounding earthquakes may be unreliable.
As mentioned previously, earth lights including EQLs overlap with reports of UFOs and spook lights. The association with paranormal or supernatural beliefs means several scientists will steer clear of such anomalies. The paranormal taint may also prevent reputable investigation into these observations which deserve some attention. Note how seriously the public takes reports of strange lights and how most scientists will brush these concerns away as mistakes. People will still seek out information, and if there are no reasonable explanations provided, the public (and media) will pick up on non-reputable explanations. Considering all this, changing scientists’ perception of EQLs is a tough goal.
Establishing the validity of EQLs
The first task to establish the validity of EQLs is to get more reliable data to build the case that they are feasible. There is a lack of facilities to record EQLs or other environmental anomalies. There is insufficient instrumentation to cover large areas for the various parameters that could be measured. Systems designed to detect anomalous fields must be able to distinguish normal fluctuations from anomalies that may be precursors. Quakefinder in Palo Alto, who works in association with Dr. Freund, is a private venture deploying magnetometers. Their goal is to get those large data sets, look for statistical significance, obtain calibrated local background measurements, and get past the anecdotes.
Much related work is going on in earnest in other countries. Cooperation is necessary. Bigger, more robust data sets, and subsequently better results can help bring additional resolution to the picture of all that may happen prior to a quake. Other countries and scientists of other disciplines are moving down this path of exploration.
In conclusion, there is much we don’t yet know about what happens prior to earthquakes. If precursors exist, they can be used to provide some warning – if not perfectly reliable in all cases. Reports of EQLs will remain unconvincing to scientists (but a fascination to the media and public) until more credible evidence is produced. The uncritical and unsophisticated promotion of EQL phenomena on the internet will lead to additional hoaxes and misidentification, making the subject more muddled. Other related observations such as ionospheric anomalies, electromagnetic anomalies, radio frequency interference, infrared anomalies, groundwater changes, and increased radon emissions also need more robust data sets and analysis. There’s a lot of work to do and it’s costly in terms of money, time, and effort.
Mainstream seismologists may be looking in the wrong place or not looking at all for those whispers from the earth that tell us something is about to happen. I’m excited about what will happen with this field of research in the future. Perhaps the next big quake will bring more convincing evidence that mysterious and spooky EQLs are genuine warning beacons that we should watch for and heed.
See me give this talk at the Goddard Scientific Colloquium on March 28, 2018.
1. St-Laurent, F., Derr, J.S., & Freund, F.T. (2006). Earthquake lights and the stress-activation of positive hole charge carriers in rocks. Physics and Chemistry of the Earth. 31, 305-312.
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Mexico “earthquake lights” of 2021
An earthquake of magnitude 7.0 occurred 11 miles (17.7 km) northeast of Acapulco, Mexico on the evening of September 7, 2021. As usual, the event was followed by personal videos flooding social media showing people scrambling outside. The sky is full of light bursts. Quickly, the media reported that these were “earthquake lights” or “rare lightning” (as reported by Reuters).
In footage from Acapulco, the flashes start shortly after the ground starts shaking, illuminating previously darkened hills behind the ocean bay and at one point appearing to bathe buildings on the shoreline in bright light.Reuters news
In Mexico City, panicked residents tried to keep their balance outside an apartment building while the sky flashed blue, white and pink, another video on social media showed.
The sources seemed to do a poor to nonexistent job of critically assessing this information and took the opinion that these flashes were unusual or natural. Maybe it’s because earthquake lights sound plausible and are a dramatic explanation for the flashes. But there are three specific reasons why we can reasonably conclude that these flashes were NOT earthquake lights. 1. They appear to be along the horizon, not high in the sky. 2. They occurred after the quake, sometimes minutes later. 3. They are not the typical and unique descriptions of earthquake lights as glows, balls, or unusual sparks, curtains or flames.
Instead, these flashes are almost certainly from arcing wires from electrical lines that are broken or touching each other. Or, they are electrical transformers that have been damaged and emitting flashes. They can also be normal lightning flashing. Due to most reports being in Spanish, I’m not readily able to tell if a thunderstorm was occurring but it is visibly raining in some news videos. So, a thunderstorm is also a possible explanation. If so, that event is unconnected to seismic activity.
A final point: it’s absurd to report on earthquake lights as if they are a regular occurrence. If they exist at all, they are very rare and our documented evidence for them is scant and questionable. Usually, the evidence is only eyewitness accounts. If these flashes were anomalous, and indicative of earthquake lights, that would be huge news. However, like other recent quakes that follow the same pattern of flashing lights immediately after shaking, we know these are not anomalies.
If people have recordings of pre-earthquake glows, lights, or other anomalous phenomena, I’d love to hear it. But so far, I see no evidence of earthquake lights in these post-quake videos. Do not assume that news sources, even normally reliable sources are scientifically informed on this niche subject. If the reports are simply repeating accounts that have someone’s personal opinions embedded in them, that’s not factual.
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