Don...Yeah, that caught my eye also. Casually, it seems like California, or parts of California, have periods when there are lots of M2s and 3s and then periods where there are far fewer. I don't think anyone understands why this should be....I guess the first step is to document whether this is real or just what you would expect by some random variation...but you would think the smaller quakes should occur at a fairly uniform rate if there are no larger (M4+) quakes to cause aftershocks and triggering...
As usual, making graphs of quakes vs date is the visual way to look at this.
Chris