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Scientists have found a link between strong tides and monster earthquakes

Written by
Brittany Martin

High tides that swell the Pacific may well be linked to stronger earthquakes, according to new research. Earthquakes are caused by tectonic plates colliding and what starts out as a smaller quake might be pushed up in magnitude by the additional pressure of a strong tide. The study out of the University of Tokyo finds that relationship results in what appears to be a statistically significant increase in strong earthquakes during periods of strong tides, according to the LA Times

Recent major seismic events—like the 9.1 magnitude earthquake that hit Indonesia and the 8.8 magnitude earthquake in Chile—have hit around full moons, when tides are strongest and, therefore, the stress from those tides is greatest. That correlation could give scientists an advantage in predicting a quake that hits during those peak tides might be more damaging than if it hit during lower tidal periods.

Unfortunately, that advantage might still be a small one, at least based on what is currently known. The additional push that comes from tidal forces only accounts for about one percent of the tectonic energy of a given earthquake.

“Earthquakes are a nearly random process. Tidal forces are just a factor in a complex process. There are lots of other factors,” Nicholas va der Elst, a geophysicist with the U.S. Geological Survey told the Times after reviewing the University of Tokyo study’s findings.

While the correlation between strong tides and big earthquakes seems to be solid, it leaves open a question of why there is no similar link seen with weaker ones. While a push from tidal forces can tip an already-powerful quake to become a "monster," it does not seem to be the case that a smaller earthquake is likely to level-up just because of strong tides.   

In other words, just because the moon is full doesn’t mean you should be dramatically more braced for the Big One than any other night—a quake of any strength could still hit at any time, regardless of tidal forces. Just know that if it does hit during those times of tidal stress, the results may be all the more devastating.   

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