Environment & Science

San Andreas fault might be stronger than we thought, new study suggests

PARKFIELD, CA - SEPTEMBER 30:  The Parkfield Coalinga bridge crosses over the San Andreas fault on the Parkfield Coalinga Road on September 30, 2004 Parkfield, California.  The tiny central California town with a population of 19 which claims to be known as
PARKFIELD, CA - SEPTEMBER 30: The Parkfield Coalinga bridge crosses over the San Andreas fault on the Parkfield Coalinga Road on September 30, 2004 Parkfield, California. The tiny central California town with a population of 19 which claims to be known as "The earthquake capital of the world" was hit with a 6.0 earthquake on Tuesday September 28, 2004. (Photo by David Paul Morris/Getty Images)
David Paul Morris/Getty Images

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The San Andreas fault is already the biggest, baddest earthquake threat in the region, but new research from Caltech suggests it might be even more dangerous than we thought.

The study, published Thursday in the journal Science, suggests that the amount of energy stored in the fault might go beyond what traditional quake models would predict.

An earthquake happens when two massive plates of earth’s crust rub against each other and get stuck. As they try to push past each other, they build up tension until finally they snap and release a whole lot of shaking.

Deeper in the earth it’s much hotter, so the plates aren't as solid and strong and don't stick with the same force. They can lock up for a short time, but before long the pressure is too much and they release their energy with tiny quakes in a phenomenon known as microseismicity.

Caltech researcher Nadia Lapusta says that’s what we see happening regularly on stretches of the San Andreas fault north of Southern California.

But when you look at sections running through the Mojave Desert and Coachella Valley, she says, "the fault is just silent ... and so you have to ask why?"

Using computer models and data from real quakes, Lapusta and her co-author, Junle Jiang, developed a theory to explain this eerie absence of small quakes.

They hypothesize that the stiff, strong portion of the plates that locks up is much deeper in those areas, extending down to the zone where micro-quakes tend to occur.

If that's true, then more stress could be building up, leading to potentially larger quakes once the fault ruptures.

Researchers currently think the portion of the fault running through Southern California is capable of about a magnitude 8 quake. Lapusta thinks even under this new model that wouldn't change dramatically.

"Under no circumstances does this imply going from a magnitude 8 to a magnitude 9," she explained.

However, she thinks it could mean slightly stronger quakes that rupture across a longer stretch of the fault, causing more damage to more areas nearby.

More research needs to be done to see exactly how much stronger the fault would be in specific areas.

Still, it's another good reminder that Southern California is living with a ticking time bomb in its backyard. Time to make sure that quake kit is ready.