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4.3 Earthquake Near San Ramon Shakes Wide Area Of East Bay

SAN RAMON (CBS SF) -- An earthquake, measuring a magnitude 4.3, rumbled through the San Ramon area Monday afternoon, shaking up local residents but causing no major injuries or damage.

The quake hit at 1:11 p.m. and was centered about seven miles east of San Ramon, according to the U.S. Geological Survey. The epicenter was just west of the Los Vaqueros Reservoir. The initial jolt was followed 13 minutes later by a 3.5 magnitude aftershock.

Shaking was felt in a wide area of the East Bay; people reported feeling it as far west as San Francisco, as far south as Menlo Park and as far east as Tracy.

"All I heard was one loud BANG, then my entire 2-story house shook. Multiple tremors," tweeted one San Ramon resident.

The USGS said the quake hit on the Greenville Fault, a right lateral strike-slip fault much like all the other San Francisco Bay Area faults. The area has always been seismically active, with a swarm of small quakes rattling the area in 2015.

"This fault is a little more quiet than the other ones. It has experienced a 5.4 and 5.8 in 1980, so no stranger to moderate sized earthquakes," said USGS scientist Ole Kavel of the Greenville fault. "There has already been one small aftershock. So we're keeping an eye in this."

The strike-slip fault moved about five inches — eight miles deep. USGS scientists believe this earthquake will follow the standard pattern of a main shock, followed by a series of aftershocks.

Kavel said unlike the earthquakes in Ridgecrest, this doesn't appear to be a precursors to a larger shake, though there is a 1 in 20 chance.

"It's about a week after the earthquake itself within the immediate vicinity of the original earthquake - after that the probabilities go down to much small numbers and it continues to decay after that," Kavel said.

While here was no major damage, the quake did shake up local residents.

"It's been a while since I felt on earthquake," Melissa Miller, who lives in Pleasant Hill, told KPIX 5. "I noticed that the lamps on my table were shaking and my cat was going a little crazy. That roll-jerk kind of thing we feel when we have earthquakes."

Sarah who lives in Fremont was also jolted.

"I felt it really strong," Sarah who lives in Fremont told KPIX 5. "The building was rolling and it kept going. It didn't stop, it was a longer one."

This was Gracie's first earthquake. She works at Ace Hardware in Blackhawk and said she thought it was a truck rolling through the hardware store.

"I was upstairs and it felt like a machine driving through the store," she said.

The moment the shaking ended, kids at the School of Imagination in Livermore left the school with teachers and crossed the street to safety.

Officials said the kids enjoyed a nice walk on a beautiful day and credited the school's bi-monthly earthquake drills to how efficiently the students were evacuated.

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