A new study has dismissed the popular theory that stated massive earthquakes across the world are triggered by a full moon. The theory or popular belief suggested that the moon or sun might trigger massive earthquakes.
However, Susan Hough, a seismologist at the US Geological Survey, has matched the dates of around 204 large earthquakes dating back to the 1600s and found no significant pattern between the quakes and the moon's phase.
Hough's discovery was published in Seismological Research Letters. In her study, she dismissed the theory of large earthquakes affected by the moon's phase, but she also said the moon does contribute to earthquakes.
"The moon does effect earthquakes to a small extent, but you can't hang your hat on it as a prediction method," she said. Hough said the linking of massive earthquakes with a specific lunar cycle is "no different from the kinds of patterns you would get if the data are completely random."
Hough decided to study powerful earthquakes to avoid detecting the clusters of quakes within the data. She thought there would be fewer chances of larger earthquakes being an aftershock of a bigger earthquake.
Her analysis showed that certain days of the lunar cycle and the larger earthquakes did match. But to find out any significance in the patterns, she randomised quake dates to find similar patterns in the random data.
"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," Hough said.
She noticed unusual "signals" in the original data. For instance, the maximum number of earthquakes – 16 – recorded in a day came seven days after the new moon. However, she said the "the signal was not statistically significant, and the lunar tides would be at a minimum at this point, so it doesn't make any physical sense."
According to Hough, the moon and sun do trigger solid-Earth tidal stresses — ripples through the planet that "could be one of the stresses that contribute in a small way to earthquake nucleation".
"Some researchers have shown that there is in some cases a weak effect, where there are more earthquakes when tidal stresses are high," she said, adding, "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."