Southern California is on alert after a recent string of almost moderate earthquakes shook the Salton Sea. Almost moderate. They weren’t big, and they certainly didn’t lead to any catastrophic damage in the area. So why are seismologists so concerned for the future of the San Andreas fault? Well, after nearly 24 hours, about 200 distinct seismological occurrences were recorded. That’s a lot of quakes.
Does it mean that the big one is coming? No, not quite. But it’s certainly cause for concern. Here’s why!
The San Andreas likes to scare us every so often. You know, with damage and noise and stuff.
In 1932, sensors were installed to detect seismological occurrences. In all the time since, only three instances of such “earthquake swarms” have been recorded. And the other two were very recent in 2001 and 2009. The “Big One” didn’t happen after either of the last two swarms either (obviously).
So why all the fuss?
Well, here’s the rub: historically, the southern portion of the San Andreas fault ruptures in a relatively predictable pattern, i.e. every 150 to 200 years. The last time it ruptured was around 1680. The current year is 2016. Subtract one from the other and you get 336 years. Subtract, let’s say, an average of 175 years from 316 and you get 161.
In other words, we’re roughly 161 years overdue for one of the most devastating earthquakes Sourthern California has ever known. That’s a really, really, really long time. A rough pill to swallow if you live in the area. (Admittedly, I used to live in the LA area and the prospect of the Big One greatly excited me. But we’re talking about normal people, so, oooo! Big crash! Loud noise! Everything go boom! Lots of money down the drain! Scary stuff.)
Add to all that the people who are still confused about how tsunamis occur, and you have a lot of paranoia at the moment. Without getting technical, these faults won’t produce tsunamis even if one were to rupture out at sea. Yay! That means the San Andreas can only hurt us so much. Japan still has it way, way worse.
Okay, sure thing. But what are the actual chances of the Big One over the near few days?
All right, so seismologists aren’t exactly in agreement about the chances that this string of earthquakes could lead to the big one. According to the U.S. Geological Survey, the chances of a 7.0 quake or higher as of this even are somewhere between 1 in 100 to 1 in 3,000 over the next seven days. The numbers don’t exactly provide one with confidence that the scientists can accurately predict the next earthquake. That’s because they can’t. According to them, the chance during any other week is about 1 in 6,000.
Maybe it is.
Think of how often the weatherman gets the forecast wrong. “Tomorrow, we’ll be getting about 24 inches of snow, so stay indoors unless absolutely necessary.” And then the scattering of flurries comes. Earthquakes are a lot harder to predict.
Anyway, so the point isn’t so much that the Big One won’t happen in the next few days. It might, or it might not. The point is this: be vigilant. Sooner or later, it will happen. You shouldn’t be paranoid that it’s coming, you should be prepared for when it does.