An earthquake that struck at 11:42 a.m. Tuesday, with an epicenter near South San Jose, gave a good shake to San Francisco and much of the Bay Area.

Did you feel it? The USGS puts the magnitude of the initial quake at 5.1, which is sizable by any standard — and one of the largest quakes to hit the region since 2014's Napa earthquake, which was a 6.0M.

There was also a 3.1M aftershock that struck five minutes later, at 11:47 a.m.

These quakes follow a smaller one, a 2.7M quake, that struck in the same area near Morgan Hill on Sunday morning.

All three of these earthquakes were on the Calaveras Fault, as NBC Bay Area explains, which last saw a large quake — a 5.4M — in 2007.

The SF Fire Department tweeted that no damage was reported in San Francisco as a result of the quake.

As per procedure, all BART trains were halted, and BART tweeted, "Expect major delays systemwide while we follow our safety procedures."

Many in the region are reporting that the earthquake early-warning system worked and texts were received. Did you get one?

We'll update you as any further details arrive.