definitely know your terrain and preferred routes. My greatest concern in a mega-quake is faults severing roads. The San Andreas in the L.A> area basically runs along the 138 in antelope valley. The aqueduct basically runs on top of it / alongside it too. So a big quake there is going to make a mess and might well cut off most of the routes north out of L.A. Which is terrible news for us, as we're just a few miles south of that fault, on the north edge of L.A. I really want to get as far away from L.A. as fast as I can in a major disaster. Several millions and not more than 3-4 days of food and water for them at hand, ever. And pretty much zero in the way of emergency supplies for them, in govt hands.
/Really don't want to be in CA at all anymore, for several reasons
eta Took the local CERT training in January this year, ironically starting on the anniversary of the Northridge Quake, and the city management folks basically told us they have a couple shipping containers with a bunch of stuff but that is for 'continuance of government' (personnel). That the general population is on their own. There's 10M people in L.A. County, and nearly that many more in all the other SoCal counties. Not including the ~2M jammed up against the southern border. There's ever a huge quake event around here, I'm running as far from all those hungry mouths as I can get. FEMA says 'keep three days of stuff', few do. And our grocery supply chains don't either.