Magnitude 3.7 earthquake beneath SFO in Millbrae rattles Peninsula

Mild quake rattles Peninsula eliciting wows and ho-hums but no damage

MILLBRAE -- An earthquake with a magnitude of 3.7, centered near San Francisco International Airport, struck the Bay Area about 6:38 p.m. Friday.

The quake occurred about 1.3 miles north-northeast of Millbrae at a depth of about 8 miles, the U.S. Geological Survey said.

The agency initially evaluated the temblor at a magnitude of 4.0. It was downgraded to 3.9 and later revised to 3.7.

Magnitude 3.7 earthquake below San Francisco Int'l Airport on Oct. 27, 2023 KPIX

The quake was centered practically underneath the San Francisco International Airport. Officials at the airport confirmed that a safety check of all the runways had already been completed and there were no issues.

The temblor was felt as far north as Santa Rosa, as far south as Santa Cruz and as far east as Tracy, according to a map posted on the USGS website.

On social media, a number of people confirmed feeling the earthquake across the Peninsula, including in Redwood City, San Mateo and Saratoga and there were also reports from the South Bay as well as the East Bay in Hayward, Richmond and Walnut Creek.

BART reduced speeds to complete track safety inspections. Riders were told to expect residual delays of up to 20 minutes systemwide.

There were no immediate reports of damage.  

The temblor was felt as far north as Santa Rosa, as far south as Santa Cruz and as far east as Tracy, according to a map posted on the agency's website.

The quake was strong enough to rattle dishes in San Francisco's Nob Hill neighborhood.

It was not strong enough to set off cellphone alerts, which are triggered by events of 4.5 magnitude, the USGS said.

In San Francisco's Castro District, some didn't feel a thing. Others like Marti Diehl noticed a slight shake as she enjoyed cocktails at a local bar. 

"I was sitting on the bar stool and I was just starting to stand up and I went (shakes) and he was next to me. I said 'did you feel that?' and he said 'Yep!' ... It wasn't the drinks," she told KPIX.

Renner, who sat next to Diehl added, "Kind of a shift. One big shift off to the side and a couple of rocks back and forth. Other people didn't even notice but we looked at each other and said did you feel that?"

For many, the ground movement was so subtle it was hard to tell it was an earthquake.

Marti Diehl has lived in San Francisco for 75 years and remembers the deadly Loma Prieta earthquake in 1989. Friday's little jolt is one she'll take any day.

"We'd rather have the teeny ones than have the big guy, you know? It's what we live with."

AFTERSHOCKS

An aftershock of magnitude 2.2 was reported at 8:24 p.m. at the Millbrae epicenter, at a depth of 7.6 miles.

Quakes of magnitude 2.9 and 2.1 were reported 6.8 miles east-southeast of Alum Rock, at a depth of 4.8 miles, at 8:21 p.m. and 8:32 p.m., respectively.

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