Deadly earthquakes do not hit during certain phases of the Moon, study finds

The infamous idea of massive earthquakes hitting during certain lunar phases or time of the year has finally been debunked with some new evidence, according to a study published in Seismological Journal Letters.

For years, people have believed that strong earthquakes happen during full moon or new moon when Earth's position is aligned with the Sun and Moon, driving a tidal rise. The idea has led to a lot of debate, but now, a scientist from US Geological Survey has given some statistical evidence to prove that there is no way the earthquakes are linked with the Earth's relative position to the Moon or the Sun.

Susan Hough debunked the infamous theory after conducting a detailed analysis of 204 deadly earthquakes that happened over the past four centuries, reports Phys.org.

The scientist focused specifically on earthquakes of magnitude 8 and above to keep any kind of minor temblors or aftershocks of a bigger quake out of the study. Then, she looked at each of those quakes by keeping the day of the year and the lunar phase for that day in perspective.

Matching the three factors did not reveal any pattern that could indicate a link between earthquake rates and lunar phases. She also noticed some weird signals such as 16 earthquakes, the highest on a single day, which neither saw a full-moon phase nor a new moon — the key factors of the so-called earthquake lore.

"My statistical analysis showed that this apparent signal is not statistically significant," Hough told CBC News while noting that lunar tides would have been at a minimum at that point. "But there's so much lore about earthquakes and full moons; I was a little surprised that earthquakes have bunched up on a day about which there's no popular lore."

Hough even randomised the dates of the earthquakes to see if there was any pattern that linked the quakes to moon's phases. The patterns showing up in the random set of data were also similar to the original dataset. "When you have random data, you can get all sorts of apparent signals, just like when you flip a coin, you sometimes end up with five heads in a row," she said while describing the finding.

Noting past studies, Hough said that Earth's tidal stresses, meaning ripples that form through Earth's surface and not in the waters because of the Sun and the Moon, could be one of the factors contributing to large earthquakes.

"There is in some cases a weak effect, where there are more earthquakes when tidal stresses are high," she said. "But if you read those papers, you'll see that the authors are very careful. They never claim that the data can be used for prediction because the modulation is always very small."

The scientist says massive earthquakes with no fitting lunar phase pattern would go unnoticed but when a deadly quake strikes on a full moon, the lore will crop up again. However, this time, her statistical study would be there to prove "that over time, there isn't a track record of big earthquakes happening on a full moon", she noted.