any disaster preparedness will tell you to always have a full tank of gas and cash (includeing coins) as one of the MANY things you should have at a moment's notice.
i got so freaked out by katrina that i bought my so cal earthquake kit and i'm passing out printouts from the LAFD website on how to shut the gas off to our buidling (so it doesn't fucking explode after the big one)
there's a VERY sobering pdf link on here:
http://www.lafd.org/disaster-prep.htm