CBS SF) — The fault that produced a 4.0-magnitude earthquake in Fremont early Tuesday morning is expected to produce a major earthquake “any day now” and Bay Area residents should be prepared, a U.S. Geological Survey scientist said.
The 2:41 a.m. earthquake on the border of Fremont and Union City
occurred on the Hayward Fault at a depth of 5 miles. The epicenter was
at a spot just north of the intersection of Niles Canyon Road and
The quake caused some BART delays early Tuesday while work
crews checked the tracks, but appears to have caused no major damage. At
least 13 smaller quakes or aftershocks had been reported near the same
location as of 6:42 a.m., the largest of which was a 2.7-magnitude at
While damage from the quake was minimal, scientists warn that a much
larger one is expected on the Hayward Fault, which extends from San
Pablo Bay in the north to Fremont in the south and passes through
heavily populated areas including Berkeley, Oakland, Hayward and
The last big earthquake on the fault, estimated to have a 6.8-magnitude, occurred in 1868, according to the USGS.
It killed about 30 people and caused extensive property damage in the
Bay Area, particularly in the city of Hayward, from which the fault
derives its name. Until the larger 1906 earthquake, it was widely
referred to as the “Great San Francisco Earthquake.”
“The population is now 100 times bigger in the East Bay, so we have
many more people that will be impacted,” said Tom Brocher, a research
geophysicist with the USGS.
“We keep a close eye on the Hayward Fault because it does sit in the
heart of the Bay Area and when we do get a big earthquake on it, it’s
going to have a big impact on the entire Bay Area,” Brocher said.
While a 2008 report put the probability of a 6.7-magnitude or larger
earthquake on the Hayward-Rodgers Creek Fault system over the next 30
years at 31 percent, Brocher said the reality is a major quake is
expected on the fault “any day now.”
“The past five major earthquakes on the fault have been about 140
years apart, and now we’re 147 years from that 1868 earthquake, so we
definitely feel that could happen any time,” Brocher said.
Brocher urged residents to take steps to prepare for a major earthquake.
The USGS shake map shows residents in the areas close to Fremont and
Union City experienced light shaking in Tuesday morning’s event, while
weaker shaking might have been felt in areas as far south as Santa Cruz,
up the Peninsula and as far east as Livermore.
Residents throughout the Bay Area reported feeling the quake, with
responses concentrated in the East and South Bay, according to the USGS.
Brocher said Tuesday morning’s 4.0 earthquake was not likely to have
much of an impact one way or the other on the likelihood of a major
earthquake occurring on the same fault.
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