No Link Between 'Super Moon' and Earthquakes

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The moon is approaching its full phase at a time when it is also at its closest position to the Earth, an event known as "maximal perigee." NASA
NASA

THE GIST

- Tonight, the moon will make its closest approach to Earth in 18 years.

- Many are worried that such an event might cause a major earthquake, or that it might have caused the Japanese quake last week.

- However, experts know of no link between the moon and major earthquakes on Earth.

Tonight's rare lunar occurrence, when Earth's natural satellite is only a mere 356,575 kilometers out in orbit, brings the moon to its closest position to Earth.

This phenomenon of extreme proximity, known as 'maximal perigee,' only occurs once every 18 years. In addition to appearing to be uncommonly big to stargazers, the moon will also be in its full phase. However, what some might see as an interesting astronomical event raises concerns for others.

Despite opinions being dispersed over the Internet that the 'super moon' will lead to natural disasters such as earthquakes, floods and volcanic eruptions, geologist Bill Burton with the US Geological Survey says that this is unlikely.

"There are just too many factors that go into seismic activity to make that statement," Burton told Discovery News. "I think you'd be hard pressed to see a difference in tectonic activity during different lunar phases."

Severe natural disasters such as the earthquake off the coast of Japan last week can raise questions about all of the factors involved. Research geophysicist Malcom Johnston with the USGS says that blaming such events on the moon's orbit is not a new idea.

"This idea of blaming natural disasters on the phases of the moon goes way back to the Greeks. It has been around for hundreds and hundreds of years," Johnston said.

These ideas, Burton adds, are largely unfounded. He noted, however, that a higher tide does have a very slight effect on tectonic activity.

"Obviously the oceans are affected by the moon; whether it causes earthquakes is under debate," Burton said. "Some minor, very shallow quakes might take place during full tide and perigee."

He explained that an increase in water pressure caused by the lunar phases might cause very minor tremors, but only if other conditions were already aligned for an earthquake to occur. Seismologists theorize that the higher tide could cause an earthquake to occur just a few days or hours earlier than it would have at normal tide.

"This might be the little push that would cause the tectonic plates to slip," Johnston told Discovery News. "Overall, the effect is negligible. But if you take data on ten thousand earthquakes, you can show there is a significant correlation between minor quakes and where the moon is in its orbit. Looking at one quake, no."

While the phases of the moon might have a minimal effect on small movements of the tectonic plates, Burton says that the correlation with major seismic activity is near nonexistent. He also stressed that the upcoming maximal perigee had nothing to do with the events in Japan.

"The Japanese quake didn't occur while the moon was close to Earth at all, so we can't link those events. It occurred a week before the lunar perigee, while the ocean was at weak tide."

Burton predicts that the only earthly change that will occur because of the moon's increased proximity will be a slightly higher tide.

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