None of them did any damage, but the ground has been busy. Between Wednesday afternoon and early Thursday, the U.S. Geological Survey recorded three earthquakes of magnitude 2.6 or larger in the Bay Area and the hills just south of it. The one most people noticed hit near Pacifica during the evening commute.
Pacifica, Wednesday 5:17 p.m.
A preliminary magnitude 2.7 quake struck at 5:17 p.m. Wednesday, Oct. 28. NBC Bay Area, citing the USGS, reported that it was centered 1.3 miles northeast of Pacifica, 3.2 miles west of San Bruno and 3.9 miles west-southwest of South San Francisco. The USGS event page puts the depth at about 6.5 kilometers, roughly 4 miles. That shallow location under a populated part of the Peninsula is why it was widely felt for its size: by Thursday morning the USGS had logged 514 reports through its "Did You Feel It?" system.
South of Hollister, twice
Two more small quakes hit the same patch of ground in San Benito County. The first, a magnitude 2.6, struck at 4:29 p.m. Wednesday. The second, a preliminary 2.7, hit at 5:38 a.m. Thursday. NBC Bay Area reported that it was centered 7.3 miles southwest of Ridgemark and 8.4 miles south-southwest of Hollister. USGS data place both at about 9 kilometers deep and within a few hundred meters of each other. The USGS logged only a couple of felt reports for the Thursday morning quake, which is not surprising given the rural location and the hour.
Should you worry?
Quakes in the magnitude 2 range are common in Northern California and rarely cause damage. Their main value is as a reminder. If one rattled your windows this week, it's a good time to check that your emergency kit has water, a flashlight and any medications you need, and that heavy items are secured. You can report shaking for any quake on the USGS event page, which helps scientists map how strongly it was felt.