That’s because Earth is under additional stress when the sun and moon are aligned and tugging in gravitational unison, as happens during those lunar phases. The team, whose research appeared in Nature Geoscience in September, also found that the biggest fault lines are most vulnerable, and more likely to slip and start moving under the extra pressure. But these are still tiny effects on the complicated whole-Earth system. Many factors can cause the ground to start shaking.
John Vidale, a seismologist at the University of Washington, says the find won’t be a silver bullet for predicting earthquakes, but it may help scientists like him understand the big picture more accurately. “Maybe we can say [a given area is] 10, 100 or 1,000 times more dangerous than usual, but that’s still only a 2 percent chance of an earthquake happening any given day or week.”