People say they felt a sharp jolt that lasted about seven to 10 seconds, but residents felt different degrees of shaking, depending upon where they were located. Some in downtown Napa say they barely felt it, while people in the northern part of town say they definitely felt the earthquake.
Napa resident Sandy Schieck says she felt two jolts. She told ABC7 News, "The first one, I got up out of the chair, had time to say, 'That was an earthquake.' I heard the metal and pans behind me starting to make noise and the second jolt came. It was kind of like a rolling jolt but enough to make everything here rattle."
So far, the Napa County Sheriff's Department says it has received no reports of damage or any injuries. It was nowhere near the magnitude 6.0 quake that struck last August that caused widespread damage. Still, it was enough to rattle some nerves.
A USGS research geophysicist we spoke with said it is possible there could be a cause-and-effect relationship between Thursday night's earthquake and the big Napa earthquake that happened.
Some of the differences though were this quake happened north of the Green Valley fault, north of the Napa quake and further east, in the hills. But it did have the same strike-slip motion consistent with the area.
It is possible this was just another quake or the 6.0 Napa earthquake could have set the stage for Thursday night's shaking.
USGS research geophysicist Brad Aagaard said, "The stresses did change as a result of the Napa earthquake. At this point we don't have the models updated to see whether this was an area where the stress was increased or decreased."
Aagaard said more than 2,000 people reported feeling the quake on the USGS website.
Three-hundred people suffered injuries in the earthquake last August and more than 1,000 buildings were damaged. The wine industry was hit hard as wineries in Napa County suffered at least $50 million in damage.
You can find guidelines for stocking an earthquake survival kit and developing an emergency plan for your family here at Prepare NorCal.
Click here to track the latest earthquakes here in the Bay Area and around the world.
Earthquake.. Great way to welcome me back:)— Janissa Gjertsen (@GJanissa) May 22, 2015
Experienced a car accident and an earthquake in the same hour. What is tonight.— Sav Grable (@ItsMeSavG) May 22, 2015