Swarm of over 30 earthquakes strike near San Ramon, strongest being 4.2: USGS

SAN RAMON, Calif. (KGO) -- Dozens of earthquakes shook the Bay Area Monday morning as a swarm of temblors struck near San Ramon, according to the U.S. Geological Survey.

The largest was a 4.2 magnitude centered in San Ramon that hit at 7:01 a.m. This followed a 3.8 quake that struck at 6:27 a.m., amid a flurry of over 30 quakes.

USGS said the 4.2 quake was about 9.4 km in depth.

On Monday afternoon, there were more earthquakes, according to USGS. A 2.5 at at 2:06 p.m., a preliminary magnitude 3.1 at 2:56 p.m., 3.0 at 3:04 p.m., and a reported 2.9 at 3:06 p.m.

There have been no reports of injuries or major damage.

Video from a San Ramon 7-Eleven on Kimball and Alcosta Boulevard shows products falling off shelves during one of the earthquakes.

The USGS said this swarm is likely a continuation of one locals saw over the last several weeks in the San Ramon Valley between Walnut Creek and Dublin.

On Friday, the area saw its first earthquake in several weeks, but there have been dozens of quakes since November.

Some residents and workers tell ABC7 Eyewitness News that while the number of quakes back-to-back is surprising, they are somewhat used to it.

One Dublin man said the shaking first woke him up, but that he is familiar with these swarms.

"20-25 years ago, there was one that lasted a couple of weeks. They weren't big, but just like this," he said.

Rogelio Oropeza, an employee at Bagel Street Café said they were preparing for the morning rush when the first earthquake shook the business.

"Everything is moving. The doors, the water, the soda machine, everything is moving very bad," said Oropeza.

Throughout the early morning dozens of shakes continued to hit the region. There were about 45 people in the pool at the San Ramon Olympic Pool and aquatic Park.

"The first one that hit I actually felt it rolling towards us and the pool sort of jumped a little bit and I say oh that was a nice little earthquake and maybe 5-10 minutes later the 2nd one rolled through that was sort of lower and then half a hour, 20 minutes later the big one hit and quite a few people felt that one and the building the roof sort of rattled," said Greg Lynch, Head Coach for the Masters San Ramon Pool.

The pool crew checked for issues and deemed it safe. The States office of Emergency Services is monitoring this activity.

"There is really nothing that will tell you that there's a larger earthquake on the horizon. I could tell you that anything above a 4.0 is something to definitely keep our eyes on, and definitely draws attention to, but again, we have hundreds of earthquakes in our state each year," said John Goodell, CA Earthquake Early Warning Program for California Governor's Office of Emergency Services.

The USGS said this swarm is likely a continuation of one locals saw over the last several weeks in the San Ramon Valley between Walnut Creek and Dublin.

"These earthquakes, some are going to be bigger than others, and some are going to be felt," Robert DeGroot with USGS said. "Many of them are very small. So the significance is that this particular sequence is just continuing and we know that this has happened in the past."

MORE: Prepare NorCal: Disaster Preparedness Resources

DeGroot says that it could go on for several months.

"This is not something that is necessarily significant of something bigger," he said. "In fact, there's a very small chance that something bigger will happen through this series of events. This is a very active area between Mount Diablo and Calaveras fault."

San Ramon Mayor Mark Armstrong said he too felt the earthquakes and says the city is focused on making sure it and its residents stay prepared.

"The city is closely monitoring the situation; these earthquake swarms are not uncommon," Armstrong said. "There's experts, the scientists, are tracking all this information. San Ramon's emergency preparedness systems are strong."

BART also had to slow down trains to inspect the tracks, which is normal during earthquake activity.

MAP: Significant San Francisco Bay Area fault lines and strong earthquakes
Zoom in on the map below and compare where you live to the significant faults and where strong earthquakes have struck in the Bay Area.

Stay with ABC7 News for the latest details on this developing story.

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