The San Andreas Fault Is Definitely Showing Signs Of Large-Scale Movement

Heads up, West Coasters.
An Uninhabited Aerial Vehicle Synthetic Aperture Radar image of the San Andreas fault in the San Francisco Bay area just west of San Mateo and Foster City is shown in this image released by NASA, June 17, 2009.

When the fault line starts rockin'... run for the hills!

New observations confirm that the San Andreas Fault System, the massive tectonic boundary underneath much of California, is showing definite signs of movement, according to a post at the University of Hawaii's website. 

In data collected from the EarthScope Plate Boundary Observatory, a series of hundreds of measuring stations scattered throughout Alaska and the American West, researchers have found evidence of 125-mile-wide "lobes" of uplift and subsidence -- that is, plates of land moving over and under one another.

Computer models that simulate the San Andreas Fault System have predicted this sort of crustal movement before. This new analysis is significant because it's showing motion that wasn't physically identified until now. 

Instances of uplift (in red) and subsidence (in blue) confirm researchers' predictions of motion in the San Andreas Fault System. The top image shows the lobes of movement found in real life using GPS data, while the bottom image shows the lobes predicted by an earthquake simulation model.

"While the San Andreas GPS data has been publicly available for more than a decade, the vertical component of the measurements had largely been ignored in tectonic investigations because of difficulties in interpreting the noisy data," said lead author Samuel Howell, a researcher at the University of Hawaii at Manoa. 

"Using this technique," Howell said, "we were able to break down the noisy signals to isolate a simple vertical motion pattern that curiously straddled the San Andreas fault." 

Scientists say it's crucial to monitor the San Andreas Fault because of its potential to unleash a catastrophic event on the West Coast. Past studies have shown that the fault system is currently at a "sufficient stress level for an earthquake of magnitude greater than 7.0 on the moment magnitude scale to occur."

That sort of earthquake would mean mass devastation.

What's more, the San Andreas Fault is connected to another incredibly dangerous fault line, the Cascadia subduction zone. 

"If the entire zone gives way at once, an event that seismologists call a full-margin rupture, the magnitude will be somewhere between 8.7 and 9.2," the journalist Kathryn Schulz wrote in a Pulitzer Prize-winning New Yorker article last year. "That’s the very big one."

As Howell points out, though, "it's pretty much impossible to say" when that might happen.

If all goes well, the new findings on the San Andreas Fault will let scientists use smaller lobes of vertical motion to predict more significant ruptures, as indicated in the journal Nature Geosciences.

Unconvinced this could mean disaster to come? Well, you could be making a seismic mistake. Be careful out there.