Did you feel that?
A 5.1 magnitude earthquake with an epicenter almost nine miles east of San Jose's Seven Trees neighborhood shook up the Bay Area at 11:42 a.m. Tuesday morning, according to the U.S. Geological Survey.
The earthquake was followed by a 3.1 magnitude earthquake at 11:47 a.m., and the aftershock's epicenter was 9.3 miles east of Seven Trees, according to the U.S. Geological Survey (USGS). It's unclear if the tremors caused any injuries or damage to buildings, but the USGS reported there is a "low likelihood of casualties and damage."
The earthquake occurred on the Calaveras Fault, according to the USGS, and the strongest shaking was felt from San Jose to Santa Cruz. Light to weak shaking was felt in San Francisco and as far away as the Central Valley, according to the USGS.
The last notable temblor on that fault happened in October 2007, which was a magnitude 5.4 magnitude quake named the Alum Rock earthquake. The same fault went off in 1984 with the 6.2 magnitude earthquake in Morgan Hill.
USGS estimated that the chance of an aftershock with a magnitude over 5 in the next week was less than 1%.
Just last week, the Bay Area marked the 33rd anniversary of the Loma Prieta earthquake, a 6.9 magnitude temblor that plunged the region into chaos on Oct. 17, 1989. So far, there have been no reports of major damage caused by today's quake in San Francisco.
State Sen. Scott Wiener, who represents San Francisco, was one of many to take note of the tremor on social media and express hope that a bigger temblor wasn't forthcoming.
BART officials said to expect “major delays” as it held trains for several minutes after the shake to perform seismic inspections.
The transit agency said all 57 trains in service during the quake—except those in the Transbay Tube—were held for five minutes in case the 5.1 tremor was followed by a larger one.
By 11:55 a.m., the trains started moving again at slower speeds, officials said on Twitter. The post-quake pause caused delays for most trains of about 12 to 15 minutes.
San Francisco resident Abhay Kashyap tweeted that his Ikea lamp served as an "at-home #earthquake detector."
Meanwhile, others were noting how they got advanced warnings of the quake from their phones.
Despite the strength of the initial earthquake, residents in San Francisco's Tenderloin neighborhood told a reporter for The Standard that they didn't feel anything.
Today’s 5.1 earthquake was the third-largest since 2000 to hit the area surrounding the San Francisco Bay. It shook the Sargent Fault, running beneath Santa Clara County, which was also the site of 2007’s magnitude 5.5 quake centered near East Foothills.
Another data point for earthquake followers: Three of the Bay Area’s Top 5 quakes happened in October, a prime time for “earthquake weather,” a season that has been formally debunked by USGS scientists.
Kamola Kobildjanova, who lives outside San Jose, said she was working from home when she "definitely felt everything shaking."
"I wouldn't say it felt very strong, but I grabbed both [my infant twin daughters] and went outside after it was over to wait out the possibility of the aftershock afterwards."
Kobildjanova said she may be overly sensitive to seismic activity: She is originally from Uzbekistan, a country in Central Asia that also has many earthquakes.
"There have definitely been earthquakes that I felt were stronger," she said.
This story will be updated.
Jonah Owen Lamb, Maryann Jones Thompson and Jennifer Wadsworth contributed additional reporting for this story.