Chico State geologist Ann Bykerk-Kauffman says Thursday night's earthquake was triggered by fault motion just south of Lake Almanor. She says, "We are close to the plate boundary between North American and Pacific plates, and we had a fault that moved." Bykerk-Kauffman adds that the way the quake was felt in the north state depended on it's size, and where people were located. She says it was seven miles below the earth, and a magnitude 5.7. The series of aftershocks are just smaller earthquakes, likely triggered by the big one. She says, "Anytime you have fault motion that causes the earthquake, you destabilize the rocks around it, and those rocks are going to adjust." Bykerk-Kauffman says it's unlikely that another, larger earthquake will follow this one. She says, "You could think this could be a foreshock to a more major earthquake, but we don't get quakes bigger than that. This one was a 5.7, and that's kind of large for around here."