Four segments of the San Andreas fault system in Northern California
are due for an earthquake of magnitude 6.8 or greater, including a
section that runs near infrastructure crucial to water supply in much of
the state, according to a geological study.
The Green Valley fault northeast of San Francisco between the
cities of Napa and Fairfield is poised for a magnitude-7.1
earthquake or stronger, said researchers from the US Geological
Survey and San Francisco State University responsible for the
report.
The fault is located near dams and aqueducts that supply water
from the Sacramento and San Joaquin rivers to the San Francisco
Bay area, Southern California, and the farm-heavy Central Valley.
The Green Valley fault’s last quake happened “sometime in the
1600s,” AP reported.
The northern Calaveras and Hayward faults in the eastern San
Francisco Bay area, as well as the Rodgers Creek fault to the
north, are the other segments with enough built-up tension for a
magnitude-6.8 or higher quake, the researchers found.
The study, published Monday in the Bulletin of the Seismological
Society of America, shows that California "needs to consider
more seriously" the major earthquake risks in the region,
James Lienkaemper, a US Geological Survey geologist and lead
author of the study, told AP.
A
passerby stops to take a picture of the earthquake-damaged Vintner's
Collective building on August 26, 2014 in Napa, California. (Justin
Sullivan / Getty Images / AFP)
The four segments at risk are part of the San Andreas fault
system, the point at which the western half of the state is
moving northwest away from the rest of the United States land
mass at a rate of about 2 inches per year.
In 2006, a study of the San Andreas system found that it was past
due for a major earthquake, one at least magnitude 7.0,
especially in the southern section of its reach. The southern
region of the fault has not seen a massive quake for around 300
years, the study concluded.
"The information available suggests that the fault is ready
for the next big earthquake but exactly when the triggering will
happen and when the earthquake will occur we cannot tell [...] It
could be tomorrow or it could be 10 years or more from now,"
said author Yuri Fialko, of the Institute of Geophysics and
Planetary Physics of the Scripps Institution of Oceanography at
the University of California San Diego.
Damage to a downtown building is seen after an earthquake in Napa, California August 24, 2014. (Reuters / Stephen Lam)
Researchers for the report released Monday gathered data in part
from regular readings of fault lines taken by geologists and San
Francisco State University students beginning in 1979.
