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High Tide During Full Moon Can Trigger Big Earthquakes: Study

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Experts believe that California is likely to experience a mega earthquake soon. Findings of a new study conducted by researchers in Japan suggest that the long-feared Big One, a quake with a magnitude of 7 or more, could possibly be triggered by a full moon.

Researchers from the University of Tokyo who conducted the new study said that large earthquakes are more likely during high tides, which occur twice a day. The moon's gravity pulls the Earth's ocean during high tides but twice a month, during a full or new moon, the tides are particularly high because the moon, sun and our planet line up together.

As the moon's gravity stretches and compresses water across the planet, it also pulls on the Earth's crust albeit a tiny bit and this subtle tugging could influence when critical points along fault lines would give way.

Scientists do not yet fully understand how large earthquakes happen but they may grow via a cascading process when a small fracture builds into a large-scale rupture. Rock movements triggered by the moon's gravity could be the final nudge that can set off a series of events that can create an earthquake.

Researchers said that the likelihood of a tiny rock failure to expand to a gigantic rupture increases as tidal stress levels increase. Thus, the chances of a tiny fracture cascading into a big earthquake are greater during high tides.

This is not the first time that the theory is proposed but the research, which was published in the British journal Nature Geoscience on Monday, Sept. 12, is the first to show a firm and statistical link.

For the study, seismologist Satoshi Ide and colleagues found that some of the most powerful earthquakes that recently occurred including the 2004 Sumatra earthquake, the 2010 Chile earthquake and the 2011 Japan earthquake happened during periods of high tide. Nine of the 12 biggest earthquakes on record were also found to have occurred near or on days characterized by full or new moon.

"Here we calculate the tidal stress history, and specifically the amplitude of tidal stress, on a fault plane in the two weeks before large earthquakes globally, based on data from the global, Japanese, and Californian earthquake catalogues," the researchers said.

Interestingly, the researchers did not find a link between tides and smaller earthquakes. The association was only observed for the largest quakes.

The findings may help in earthquake forecasting particularly in places where quakes commonly happen.

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