CalTech Seismologists Warn Of Potentially Large Quake From Puente Hills Fault Under LA

PASADENA (CBSLA.com) — With the amount of recent seismic activity, CalTech seismologists warn that the Puente Hills thrust fault, which runs through Downtown Los Angeles, could produce a major quake under the city.

The fault, which produced Friday's 5.1 quake, is a relatively new discovery.

"That fault was really illuminated after the Whitter-Narrows earthquake in the late 1980s," USGS seismologist Susan Hough said. "We hadn't really known about it beforehand, because it doesn't reach the surface. It's kind of hidden."

Seismologists refer to a fault that matched these descriptions as a "blind fault". Unlike most other faults, a blind fault has no visible evidence of its existence at the surface.

Furthermore, the fault branches off into many directions.

"We're really kind of caught in a vice grip because of what the plates are doing," Hough said.

Hough also says that, due in part to the fault's location, along with its potential for extreme seismic activity, the fault has the ability to cause a large earthquake.

"(It can cause) potentially a 7.5 (quake), which is the very scary, big one that we all worry about," Hough said.

Seismologists say that, due to the fault's proximity to Downtown Los Angeles, the theoretical quake could be more devastating than the 1994 Northridge earthquake.