By Southern California (click here) I mean between latitudes North 34 degrees, 32 minutes and 48.572 seconds and 47.0 North degrees
All Earthquakes in California-Nevada Map Area (click here)
All Earthquakes in California-Nevada Map Area (click here)
I believe the center of the state of California is about 37 North degrees, so that is what I called South. I suppose one can divide it until thirds, but, I did not because I have never heard the description Central California. The geological locations are am familiar with are Northern California (made popular by the Beach Boys) and Southern California.
September 22, 2012 is a random day after the Earthquake Swarm in August. Just that simple. Nothing particularly notable about that day. When one clicks on the link "All Earthquakes in California and Nevada Map Area" it is easily discerned how many quakes are occurring daily in this area of the USA. The quakes I counted could also involve the Nevada border as well.
No Rocky Mountains there.