So I just went through the catalog and documented the number of "3+" magnitude quakes to hit the Bay Area every year from 1970 through December 31st 2009. I plotted it out in Excel and found an interesting trend. For the past TEN years, the number of total quakes of magnitude 3+ have been well below the number of quakes that occurred in the prior 3 decades.

I don't know why in my head I thought activity in the area was increasing, but clearly my perceptions are wrong. So basically in the last 10 years, earthquakes in SF have been on the decline when compared to the years dating to 1970 (Maybe this weekend I'll run through to the 60s and 50s to see).