SAN RAMON (CBS SF) – Beneath the San Ramon-Danville area, an earthquake swarm erupted as high as 3.9 on Wednesday, giving locals a subtle reminder of the earthquake activity deep beneath the area.
According to the U.S. Geological Survey, a magnitude 3.9 magnitude earthquake occurred at 11:43 a.m., followed by a 2.6 magnitude earthquake at 11:46 a.m. A third 3.0 magnitude aftershock struck at 11.58. Over the last several hours, more than a dozen minor earthquakes have followed.
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Preliminary USGS data showed the quake struck an area along El Capita’s Drive, located west of Danville’s Crow Canyon Country Club near the San Ramon border.
According to the USGS, it was felt even as far east as San Francisco, north to the Valley, and south to Santa Cruz.
“Yes, here on the Oakland / Emeryville border,” Kimberly Huntimer tweeted. “It completely amazed me.”
“I thought I felt the earthquake here in San Francisco,” Mary French tweeted.
Closer to the epicenter, the vibration felt strongly.
“Yes, a lot of tremors in San Ramon,” M.Everest tweeted.
“It was very scary here in San Ramon,” Shak tweeted. “It probably took 2 seconds … it felt like a lifetime.”
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“A strong shock in Alameda,” Kimberlee MacV tweeted.
#Earthquake Johanna in Dublin tells what happened to her home. 4.0 magnitude #earthquake. 1 mile from San Ramon, California, ###United States https://t.co/TSak3MgbvI… #KPIXTV pic.twitter.com/EX2BK7sHf0
– Juliette Goodrich (@JulietteKPIX) November 17, 2021
After the quake, BART trains were held for a while and the tracks were inspected, which is the normal course of action after earthquakes.
BART is recovering from a previous problem. There is a 10-minute delay system in all directions due to a previous earthquake recorded in the BART service area.
– SFBARTalert (@SFBARTalert) November 17, 2021
No injuries or injuries were reported.
Harper Skaggs, a student at the Christian Academy in San Ramon Valley, used the skills he learned during The Great Shake Out as he and his classmates spent five minutes under their desk.
“It was strong because I was close. I was in social studies at school and I just knew everything and we had to like being under the desk, ”Harper told KPIX 5.
The USGS says the quakes and subsequent aftershocks were likely part of the Calaveras Fault system, possibly focusing on the Pleasanton fault, and that this could be the beginning of a long quake.
“The San Ramon Valley is experiencing so-called earthquake swarms, where dozens of earthquakes can occur over days and weeks,” said USGS geophysicist Brian Kilgore.
According to the USGS, there is a 26% probability that an earthquake of magnitude 6.7 or higher will occur in the Calaveras Migration over the next 30 years, but only a slightly lower probability is expected for the “Big One” in the Hayward Migration.
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Andria Borba contributed to this report.