Sunday, March 20, 2011

Predicting Earthquakes in California? I can do that too! I'll do it right now...

By golly, there is going to be an earthquake in California tomorrow! I'm going to go out on a limb and predict it. In fact, I will state unequivocally that there will be several earthquakes in California, some in the north state, and some in the south state. And I will be correct in my predictions. So, that should net me a few stories on the cable news networks, and a flood of tweets across the Internet by worried people who don't really believe it, but it could be true, you know....

What's my secret? There is no secret. California has earthquakes every day. We had 368 of them in the last week alone (368 quakes in a week is NOT unusual...sometimes there are more, sometimes there are less, but always there are hundreds). Check out the map below:

This blog was prompted by another flurry of requests from students and readers about someone somewhere predicting that we would have a big quake in California tomorrow; I won't provide links. They scare people needlessly, and it is irresponsible.

Anyone can predict quakes. But no one can predict large quakes with any kind of accuracy that will save lives. We can make long-term evaluations about the chances that a particular fault will rupture within a period of decades. But we can't predict big quakes a few days in advance. Anyone who says so is plain flat-out wrong. They will keep predicting quakes one after another, and one of these days, one of their hundreds of predictions will come true, and they will cash in.

I have a funny sense of deja vu, like we've been here before...

From my post of April 13, 2010:
8.4 Quake in California? Don't believe everything that Tweets...

No.

I should stop there, but I will say that no one can predict quakes in any useful way.

California's biggest quakes will be in the range of 7.8-8.0, quite a few times smaller than an 8.4. The stresses are there for a large quake to happen, but a magnitude 8 quake is given only a 4% chance of occurring sometime in the next 30 years.

Please don't believe everything that tweets....

But do prepare for quakes in California. They CAN happen any time, but NO ONE can predict them.

From my post of April 15, 2010:

8.4 Quake in California? Not so fast there, Twitterers...

If you have not read XKCD comics, you have been missing out on a great treat, especially if you are the scientific nerdy type of personality. On the heels of the Sierra El Mayor earthquake in Baja California, the comic above made the rounds, revealing a great truth: we are a wired, interconnected society (surprise!). Of course, there are the disadvantages as well.

So, to explain Tuesday's brief post: the XKCD comic above came true in a fashion...except there was no earthquake. I was checking my e-mails during a short break in my night class, and I had several people asking if the tweets they had received from friends were true, was the state of California declaring that an 8.4 magnitude quake would be hitting within the next 48 hours? Then I saw a few phones open up in class, and someone asked me directly about the Tweet on their phone. Clearly a rumor was spreading with the speed of electromagnetic energy and texting fingers. A hoax? An idiot crying 'fire' in a theatre? Undoubtedly. I posted my brief message explaining why the Tweet wasn't true, and had more than 2,000 hits in the space of 90 minutes. By the midnight, the 20th ranking query on Google was '8.4 magnitude earthquake in California'.

A lot of damage is done when rumors like this spread. No one can predict earthquakes, and a false prediction like this (or from 'psychics') can unnecessarily frighten people, and lead to a situation that will be perceived as crying 'Wolf'. People will stop paying attention to real warnings by qualified seismologists and vulcanologists.

We cannot predict earthquakes in such a way as to know the day, the week, or the month. We can use the history and prehistoric behaviour of fault zones to determine the possibility of a large quake within a time frame of decades. If you want a scientifically grounded prediction about earthquakes in California, check out the diagram below, from the Uniform California Earthquake Rupture Forecast (UCERF). The message to take away? Ignore the tweets, and pay attention to your personal emergency preparations. Quakes will happen.

Update #1: A nice explanation of why we can't predict big quakes can be found here.
Post a Comment