Full and new moons linked to timing of largest, deadliest quakes ...

Full and new moons linked to timing of largest, deadliest quakes
Chalk another one up for the weird effects of the moon. Full and new moons seem to make earthquakes more likely – at least the largest, most devastating quakes.
Although the effect is too small to make much difference in preparing for earthquakes in the short term, the discovery could some day provide key insights into the ways that they develop and grow.
During full and new moons, the sun, moon and Earth align, meaning that gravity tugs more strongly on the planet’s crustal plates. The resulting “Earth tides” and increased tidal movements in the oceans can add to the stresses on earthquake faults.
Advertisement
It therefore seems plausible that they might make the faults more likely to slip. A few studies have previously found hints that this might be true, but the effect of the tides has barely been detectable.
Now Satoshi Ide and his colleagues at the University of Tokyo, Japan, have found a clearer link. They analysed the size of tidal stresses in the two weeks prior to large earthquakes, with a magnitude of 5.5 or greater, over the past two decades.
In contrast, smaller quakes showed no tendency to cluster at these times.
When the researchers looked more closely, they found that on days with high stress, earthquakes are more likely to be large than at times of lower stress around the half-moon. This may be because the increased stress gives an extra boost to slipping faults, allowing a small slip to spread into a larger rupture, they suggest.
Scientific tremor
Other seismologists are cautiously excited about Ide’s results. “It’s a very interesting and intriguing observation. If it’s right, it’s a very big deal,” says Emily Brodsky, an earthquake physicist at the University of California, Santa Cruz.
However, she notes that the sample size of just a dozen earthquakes is tiny for such an important result. Seismologists may have to wait for more great quakes to see whether the pattern holds, she says.
Even if further results bear out Ide’s pattern, it may have little practical effect. The risk of an earthquake on any given day is already tiny, so a slight increase or decrease based on the phase of the moon is unlikely to alter preparations or planning, says John Vidale, a seismologist at the University of Washington in Seattle.
Instead, learning about the moon’s tidal kick-start may help seismologists understand how small ruptures progress into larger earthquakes, says Brodsky — which could eventually pay off with better predictions.