Subscribe

What’s happening with the San Andreas fault?

A new study finds that areas along the southern San Andreas fault are rising and falling, reflecting centuries-long buildups of seismic energy that could potentially trigger a major earthquake.

  • close
    Water bubbles up through the Los Angeles pavement in March 2014, following an 5.1 earthquake. A new study shows that parts of California lying along the San Andreas fault are sinking, while others are rising at the same rate.
    Mark Rightmire/AP
    View Caption
  • About video ads
    View Caption
of

Parts of California lying along the San Andreas fault are sinking, while others are rising at the same rate, according to a new study published in journal Nature Geoscience on Monday. The underlying causes of that movement, say researchers, will eventually culminate in a major earthquake.

"Once there is a major event, all of that energy gets released," said Sam Howell, the study's lead author and PhD candidate in geophysics at the University of Hawaii at Manoa (UHM), in an interview with the Los Angeles Times.

Santa Barbara and San Luis Obispo as well as parts of San Bernardino county, the study found, were among the 125-mile "lobes" where the land was rising. In Orange County, the Los Angeles Basin, Bakersfield, and San Diego County, the opposite effect was occurring, with those areas falling a few millimeters per year.

Mr. Howell added that it is "pretty much impossible to say" when an earthquake would occur next. But the study, which used GPS data from an observatory that tracks seismic information on the Pacific and North American tectonic plates, will help scientists better understand how the fault line's behavior might affect the region around it.   

"While the San Andreas GPS data has been publicly available for more than a decade," said Howell in a press release accompanying the study, the question of whether terrain was moving vertically had been ignored in previous research because of "difficulties in interpreting the noisy data." 

The vertical motion of Earth's surface is subject to local, short-term variables that often prove tough to control for in studies, such as the pumping of groundwater, local surface geology, and precipitation levels.

By making use of a new statistical technique, Howell and his team were able to "break down the noisy signals to isolate a simple vertical motion pattern that curiously straddled the San Andreas fault," he said.

In doing so, added co-author Bridget Smith-Konter, associate professor at UHM, the team was able "to confirm that the buildup of century-long earthquake cycle forces within the crust" were responsible for the pattern.

The San Andreas fault is considered California's most dangerous fault line, but the last major event along it came in 1906, when San Francisco was hit by a 7.8-magnitude earthquake. In the southern part of the fault, though, it's been about a century and a half since a big earthquake, and for areas south of Los Angeles, three centuries have passed.

Smithsonian Magazine noted in 2015 that stresses along the fault have built up over the years.

"We think Southern California is locked and loaded, that the stresses have really built up," US Geological Survey seismologist Ned Field told the Smithsonian at the time, "and when things start unleashing, they could unleash for years."

About these ads
Sponsored Content by LockerDome
 
 
Make a Difference
Inspired? Here are some ways to make a difference on this issue.
FREE Newsletters
Get the Monitor stories you care about delivered to your inbox.
 

We want to hear, did we miss an angle we should have covered? Should we come back to this topic? Or just give us a rating for this story. We want to hear from you.

Loading...

Loading...

Loading...

Save for later

Save
Cancel

Saved ( of items)

This item has been saved to read later from any device.
Access saved items through your user name at the top of the page.

View Saved Items

OK

Failed to save

You reached the limit of 20 saved items.
Please visit following link to manage you saved items.

View Saved Items

OK

Failed to save

You have already saved this item.

View Saved Items

OK