Not to minimize the consequences of a major earthquake in LA, San Francisco Seattle, Portland, or other large cities. However, one needs to keep in mind that the amount of ground breakage is very dependent on local geologic conditions, which vary dramatically in a small area. Above ground features, such as highway overpasses, are different, in that they can collapes due to the shaking itself. A runway can shake a lot and not be damaged if there isn't actual ground breakage. Certainly the damage in Anchorage from the '64 quake varied tremendously over small distances. Part of my house dates from pre '64, and was not damaged at all, so far as I know. About a quarter mile away, a whole neighborhood was totally destroyed in a landslide.

Regarding airports specifically, the control tower at Anchorage International collapsed. I'm not sure how much damage was done to the runways. I do recall reading somewhere that Elmendorf AFB (just north of downtown) was able to get recon flights into the air the day following the '64 quake, to begin surveying the extent of damage. I will try to find out more info on this.

Beacause they are designed to operate in war zones, military aircraft are a good deal more versatile than many people realize. Besides the big C5A's, there are somewaht smaller C-17's, and smaller still C-130's. Either of these can operate on shorter and rougher strips. If even a portion of the runways (or even taxiways) at SeaTac or LAX were left intact, there is a good chance these aircraft could get in. Bring in a few bulldozers in the initial loads, and even more of the runways might be put back into operation. Helo's would be essential to ferry supplies out from these airports to outlying areas. The military also has mobile teams that could quickly come set up local air traffic control to fill the gap left by destroyed control towers etc.

There is no doubt that a major earthquake under a big city would be catastrophic. And no question that people should prepare, as much as their particular circumstances permit. However, there is also no doubt that some significant help would be coming in from areas outside the damage zone.