Experts say a bigger earthquake along the lesser-known
fault that gave Southern California a moderate shake could do more damage to
the region than the long-dreaded "Big One" from the more famous San
Andreas Fault.
The Puente Hills thrust fault, which brought Friday night's
magnitude-5.1 quake centered in La Habra and well over 100 aftershocks by
Sunday, stretches from northern Orange County under downtown Los Angeles into
Hollywood — a heavily populated swath of the Los Angeles area.
A magnitude-7.5 earthquake along that fault could prove more
catastrophic than one along the San Andreas, which runs along the outskirts of
metropolitan Southern California, seismologists said.
The U.S. Geological Survey estimates that such a quake along
the Puente Hills fault could kill 3,000 to 18,000 people and cause up to $250
billion in damage. In contrast, a larger magnitude 8 quake along the San
Andreas would cause an estimated 1,800 deaths.
In 1987, the fault caused the Whittier Narrows earthquake.
Still considered moderate at magnitude 5.9, that quake killed eight people and
did more than $350 million in damage.
Part of the problem with the potential damage is that the
fault runs near so many vulnerable older buildings, many made of concrete, in
downtown Los Angeles and Hollywood. And because the fault, discovered in 1999,
is horizontal, heavy reverberations are likely to be felt over a wide area.
The shaking from a 7.5 quake in the center of urban Los
Angeles could be so intense it would lift heavy objects in the air, like the
1989 Loma Prieta Earthquake in Northern California, where the shaking was so
bad "we found an upside-down grand piano," USGS seismologist Lucy Jones
told the Los Angeles Times.
That would "hit all of downtown," Jones said.
"And everywhere from La Habra to Hollywood."
About 150 aftershocks, including one of magnitude-4.1, were
felt since Friday night's quake, which forced several dozen people in the
Orange County city of Fullerton out of their homes after firefighters
discovered foundation problems that made the buildings unsafe to enter,
authorities said.
Fire crews’ red-tagged 20 apartment units after finding a
major foundation crack, but residents have since been allowed to return.
Structural woes, including broken chimneys and leaning, were uncovered in half
a dozen single-family houses, which were also deemed unsafe to occupy until
building inspectors clear the structures. About two dozen residents remained
displaced, down from more than 80 after the initial quake.
Another 14 residential structures around the city suffered
lesser damage, including collapsed fireplaces.
A water-main break flooded several floors of Brea City Hall,
and the shaking knocked down computers and ceiling tiles, Stokes said.
It
was not immediately clear if City Hall would reopen Monday. An email to the
mayor was not immediately returned.
