Moon’s pull can trigger big earthquakes
Geologic strain of tides during full and new moons could increase magnitude of tremors.
Alexandra Witze
12 September 2016
Big earthquakes, such as the ones that devastated Chile in 2010 and Japan in 2011, are more likely to occur during full and new moons — the two times each month when tidal stresses are highest.
Earth’s tides, which are caused by a gravitational tug-of-war involving the Moon and the Sun, put extra strain on geological faults. Seismologists have tried for decades to understand whether that stress could trigger quakes. They generally agree that the ocean’s twice-daily high tides can affect tiny, slow-motion tremors in certain places, including California’s San Andreas fault1 and the Cascadia region2 of the North American west coast.
But a new study, published on 12 September in Nature Geoscience3, looks at much larger patterns involving the twice-monthly tides that occur during full and new moons. It finds that the fraction of high magnitude earthquakes goes up globally as tidal stresses rise.