Just in Time for Halloween: Full Moons Can Trigger Earthquakes

When the moon hits your eye like a big pizza pie that’s an earthquake.

Attention, moon-fearing humans: your long-held suspicion that the full moon can interfere with life on Earth seems to have a scientific basis after all. No, the moon still doesn’t make you crazy, horny, or murderous. But it can trigger large earthquakes.

Since the 19th century, scientists have debated whether the gravitational tug of the Moon and the Sun influence seismic activity here on Earth. In recent years, evidence has been mounting that the ocean’s twice-daily high tides can result in small, slow-moving tremors. But to date, this relationship has been restricted to specific environments and parts of the world, such as the the San Andreas fault in California.

Now, we have the first strong evidence for a global relationship between the larger, monthly lunar cycle and powerful rumbles within the Earth. Examining three separate seismic databases, a team of geologists at the University of Tokyo has found an overlap between some of the largest quakes in recent memory (magnitude 5.5 or above), and periods of high tidal stress, when the Sun and Moon are aligned to yield the strongest gravitational tug on the Earth. Those events include the 2004 Sumatra quake (magnitude 9.3), the 2010 Maule quake in Chile (magnitude 8.8) and the 2011 Fukushima quake in Japan (magnitude 9.0).

While the details of how large earthquakes form and evolve haven’t been fully worked out, the process is thought to involve a number of small ruptures cascading to form a really big one. Based on the new analysis, it would seem that such a cascade is more likely at the full or new moon, when the Sun and Moon are exerting the maximum amount of strain on the Earth. The authors also found that the fraction of large earthquakes compared with small earthquakes increased as tidal stress increased.

This will certainly help me adjust my travel schedule away from Los Angeles better.

While the earthquake prediction game is getting better, it’s still not much more accurate than figuring out what your adolescent daughter will be feeling five minutes from now (my daughter was an adolescent once, I know whence I speak). Still, for those of us who live in the earthquake areas, anything that might help is welcome.

That being said, I’ve been hearing since I was a kid that California is due for “the big one” any day now. For those new to my readership: I was a kid a long time ago. It isn’t that I doubt that Southern California will have another huge earthquake, it’s that I still think it is going to be a surprise.