I think Ritter has it right as set forth here:
www.equipped.org/earthqk.htm. I am dispersing my supplies throughout my property, since there may be considerable damage and some areas may be inaccessible. I just shove a few basic items under the bed, like the pry bar, kept there so I can pry my way out (In the event, AkSAR and others are welcome to pry into my affairs, likely the sooner the better).
I believe reinforced four posters have been marketed here in SoCal, but I don't think large numbers have been sold. If you have a one story framed dwelling, you are in an inherently good structure for withstanding EQs,especially if you are properly tied to your slab or foundation.
I always chuckle at the brief appearance of incredibly cheesy "survival kits" in the local big boxes following any shaking event that gets significant coverage. They disappear after a month.
I have been told that there is a dip in the housing market following something like Northridge or Loma Prieta, but that things are back to normal in about three months. Sounds about right.....
I am in the process of tweaking my EQ preps and renewing perishables.