A pair of earthquakes in quick succession Tuesday evening jolted and rattled Sonoma County, particularly in and around Santa Rosa where the epicenter was.
The first, 4.3M quake struck at 6:39 p.m., about 2.4 miles north-northeast of the center of Santa Rosa — it was given a preliminary magnitude of 4.4. The second quake, 3.9M, which at least one seismologist said was an aftershock, occurred a minute later. And while Santa Rosa residents felt the strongest jolts, the shaking was felt as far south as Santa Clara County.
Santa Rosa resident Leslie Melodia told KPIX that glassware was tossed around and broken in her home. "It was not like the '89 earthquake where it was more of a rumble. This was an actual jolt where we have cracks in our ceiling."
This was another earthquake story where the local news has images of liquor bottles broken on the floors of corner stores, and most of the damage appears to have been fairly minor. The Santa Rosa Fire Department said they were responding to multiple reports of gas leaks and stuck elevators.
Earthquake Update: Santa Rosa Fire has responding to multiple reports of odors of gas, gas leaks, fire alarms as well as stuck elevators. No reports of any injuries related to the quake at this time.— Santa Rosa Fire Department (@SantaRosaFire) September 14, 2022
USGS seismologist Austin Elliott tells ABC 7 that the quakes were on the Rodgers Creek Fault, which is part of the San Andreas Fault system.
Dr. Lucy Jones, another seismologist, writes on Twitter, "The last big earthquake on [the Rodgers Creek Fault] was in the 18th century. It has a long term slip rate just under 1 cm/yr which puts it in the same class as Hayward, Garlock or San Jacinto."
"Every quake has a 5% chance of being followed by a larger quake within the next 3 days,” Jones says. “But most are only a little bit larger. When it is right on a big fault, capable of a big quake, the chance that that following earthquake will be big is a little higher, but still small."
In San Francisco, the quakes led to more minor shaking, and if you were up and about you might not have felt it. As Twitter user foggy sunset writes, "it was a long rumble in SF's sunset district."
California's ShakeAlert early warning system seemed to function fairly well, but it didn't give much or any warning to people in Santa Rosa. As the Chronicle reports via the USGS, by the time alerts started going out, people within a nine-mile radius of the epicenter had already felt the first quake. "People in Vallejo had an 11.4-second warning before the quakes hit; San Francisco got an 18.8-second warning and Oakland residents got a 19.2-second warning," the Chronicle reports. The alert system also thought the quake was a 4.9M, but it was actually 4.3M.
Tuesday's shaking in Santa Rosa followed a smaller quake that occurred Sunday in the East Bay, centered near the Caldecott Tunnel in the Oakland hills. That quake had a magnitude of 2.9M, and appeared to have been on the Hayward Fault.
Update: Sonoma County saw another small earthquake Wednesday at 11:55 a.m., this one a 2.7M that was centered just east of the town of Sonoma.