MARCH 11, 2015
LOS ANGELES, CALIFORNIA
Scientists are virtually certain that California will be
rocked by a strong earthquake in the next 30 years. Now they say the risk of a
mega-quake is more likely than previously thought.
The chance of a magnitude-8 quake striking the state in the
next three decades jumped to 7 percent from 4.7 percent, mainly because
scientists took into account the possibility that several faults can shake at
once, releasing seismic energy that results in greater destruction.
While the risk of a mega-quake is higher than past
estimates, it's more likely — greater than 99 percent chance — that California
will be rattled by a magnitude-6.7 jolt similar in size to the 1994 Northridge
disaster. The chance of a Northridge-size quake was slightly higher in Northern
California than Southern California — 95 percent versus 93 percent, according
to a report released Tuesday by the U.S. Geological Survey.
"California is earthquake country, and residents should
live every day like it could be the day of a big one," USGS geophysicist
and lead author Ned Field said.
The latest seismic calculations largely mirror previous
findings issued by the USGS in 2008. Back then, scientists also determined that
California faced an almost certain risk of experiencing a Northridge-size
quake.
The new report included newly discovered fault zones and the
possibility that a quake can jump from fault to fault. Because of this
knowledge, the odds of a catastrophic quake — magnitude 8 or larger — in the
next 30 years increased.
There is a 93 percent chance of a magnitude 7 or larger
occurring over the same period and a 48 percent chance of a magnitude 7.5 —
similar to previous estimates.
Thousands of quakes every year hit California, sandwiched
between two of Earth's major tectonic plates, the Pacific and North American
plates. Most are too small to be felt.
Of the more than 300 faults that crisscross the state, the
southern segment of the San Andreas Fault — which runs from central California
to the Salton Sea near the U.S.-Mexico border — remains the greatest threat
because it hasn't ruptured in more than three centuries.
The report found there is a 19 percent chance in the next 30
years that a Northridge-size quake will unzip the southern section compared to
a 6.4 percent chance for the northern section, partly because it last broke in
1906.
The southern San Andreas is "ready to have an
earthquake because it's really locked and loaded," Field said.
The report is a forecast, but it is not a prediction.
Experts still cannot predict exactly where or when a quake will hit anywhere in
the world.
In recent years, the USGS and several universities have been
testing an early warning system designed to detect the first waves of a jolt
and send out an alert before the slower-moving damaging waves. Proponents have
said a few seconds of notice can allow trains to slow down, utilities to shut
off gas lines and people to duck for cover. The public alert system — still in
pilot phrase — needs more funding before it can be rolled out statewide.
Source: USGS andfoxnews.com