Large earthquakes are more likely when there are high or spring tides, ie in phases from new moon or full moon, according to a study published today in the journal Nature Geoscience.

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A team led by Japanese academic Satoshi Ide of the University of Tokyo, conducted experiments that provide practical evidence of this phenomenon, which until now intuited but without being shown.

Satoshi Ide and colleagues recreated the size and scope of the “tidal force” – an effect of gravity which is responsible for the existence of tides – registered in the two weeks prior to several large earthquakes (with magnitudes of 5.5 or higher ).

Scientists have identified a correlation between tidal forces and large earthquakes, although not having detected intensity with small earthquakes.

They showed that large earthquakes such as Sumatra (Indonesia) at 204, Maule (Chile) in 2010 and Tohoku-oki (Japan) in 2011 occurred in times of a wide range of high tidal force.

The team of researchers also found that the proportion of large earthquakes, compared to the small increases in direct relation to increases in the amplitude of the tidal force.

The science has yet to fully explain how to initiate and to unfold large earthquakes but it is believed that increase in cascade, from a fracture in a small tectonic plate which becomes a large crack.

The study authors point out in Nature Geoscience that if this is so, their study indicates that the likelihood that a small fracture spreading to become a major gap increase during high or spring tides.

As a result, a greater knowledge of the strength of tides in seismic regions may contribute to better predict the likelihood of earthquakes, argue the scientists.


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