Full and New Moons May Be Linked to Big Earthquakes

NASA Space Shuttle imagery from 2000 shows a section of the San Andreas fault in California. A new Japanese study suggests that big earthquakes may be triggered by gravitational pull from celestial bodies.

If you're a fan of classic rock, you're familiar with the Creedence Clearwater Revival song "Bad Moon Rising," in which lyricist John Fogerty warns that "I see trouble on the way / I see earthquakes and lightning."

Well, we don't know about the lightning, but when it comes to the quakes, Fogerty might have been on to something. In a study just published in Nature Geoscience, University of Tokyo researchers report that of the 12 largest recorded earthquakes -- those with a magnitude of 8.2 or more -- over the past two decades, nine occurred on days near new or full moons, when the gravitational tidal pull caused high stress across the fault.

"It's a very interesting and intriguing observation," says Emily Brodsky, an earthquake physicist at the University of California, Santa Cruz, told New Scientist. "If it's right, it's a very big deal."

As far back as the 1800s, scientists have suspected that gravitational force from celestial bodies might be able to trigger earthquakes. The theory fell into disfavor in the 20th century, but recently, researchers have found evidence of a possible link. As this 2015 Scientific American article details, Greek researchers, who analyzed 17,000 earthquakes in southern Greece between 1964 and 2012, found evidence of a link between the quakes and tidal effects of the sun and moon.

But the Japanese study provides much stronger proof of a connection.

As the New Scientist article explains, during full and new moon phases, the sun, moon and Earth align, which causes gravity to pull more strongly on the tectonic plates that make up the Earth's crust. That puts more stress on earthquake faults. It also causes increased tidal movement of water in the oceans, which adds even more stress to the faults.

If substantiated by additional studies, the effect that the Japanese researchers describe would be just one of the factors that cause major earthquakes, and it probably isn't strong enough of a factor to be of much value in making short-term predictions about when they will occur, according to New Scientist. But it would help scientists to better understand the process that results in quakes.

From Discovery News