The map (http://earthquake.usgs.gov/earthquakes/step/) as I write is back to showing high probability of severe earthquakes for the Sierra MAdre mountains reachin gfomr abive Fresno up past Grass Valley (east of Sacramento. That was how it looked when I first posted teh link. Then the forecast area shrank back to what it was yesterdy and now it is large area again.
Ben, the map is not exact, but an initial attempt to develop a probablistic means to apply known seismic hazard analysis and current activity. What you need to look at is what the map is saying. The area you are concerned about has at max about a 1 in 100 chance of an aftershock that could knock things off a shelf (Mercalli VI - Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.). A MMI VI is roughly equivalent to the shaking directly above a M4.5 quake.
So you need to scale back your interpretation of this map. It does not predict SEVERE earthquakes, only potential MMI VI damage as a statistical possibility.
Interesting.
Thanks.
And for your comments Godzilla.