Being an incurable nerd, I got an app for my i phone called Quake Watch. The daily number of very small quakes in California are amazing. Responsible are a profusion of volcanic areas and fault zones which don’t necessarily affect each other.
It does kind of bother me that while 4.4 is NOT a big quake, usually even those have aftershocks. So far this one hasn't.
It's making me a little nervous.