Obviously, the best thing to do is to raise the standard of living well above the 'line of death'. This cannot be done by aid, but by open trade and meaningful employment. Haiti's sugar and other agricultural products are blocked by US protectionism.
Better construction can shorten the initial big dip, and better planning can steepen the recovery curve. Are there cities where it is hopeless to sink a billion dollars to try to change the curve? You bet! Could I have done anything with New Orleans before the storm? My billion would have been swallowed by corruption.
Could I have done anything for Haiti? You will notice that the politicians and newspapers tiptoe around the issue of overpopulation and a certain church. If I had poured my billion into that valley of death, it would have resulted in more overcrowding, and more illegal levels being added to the existing crap buildings.
What about Padang, Indonesia? Here it is, a giant tsunami-scoop basin with no evacuation exits! Right in front, the stage is set for an M8 (or more). If it is packed to the gills, then you can't do much. If they have the income, newer buildings can be tsunami refuges, but that's a lot of money! I'm afraid a billion dollars is a bucket of water on the desert.
But you can do something about rich cities! Right now, many of them are hopelessly smug, and say something like this: "We're not California, or Haiti, so we don't have to do anything!" But so much could be done! We have a moral obligation to the world curve, to reduce massive economic loss, where we can prevent it!
So now, we are in the company of cities such as Toronto, Montreal, New York and Boston. There are many others who have the 10-3 odds of major devastation, and yet have done nothing about it. That billion dollars could go into 'earthquake awareness', and have an effect. Studies could be done, and other simple things accomplished. As I have said before, the odds are so low that each individual city will 'pooh-pooh' it, and place it below potholes, but on a world scale, this happens all the time.
In summary, a devastating urban earthquake hits somewhere in the world, every few years or so. The worst hit are the places where there hasn't been a major earthquake in 300 years, and absolutely nothing had been done in advance. Some cities may be too hopeless to do anything, but there are many places where great improvements can be made for a reasonable amount of money.