"Detroit's population has fallen by around a third since 1950 and now equals about 950,000. It is expected to shrink slowly but steadily until at least 2030; unemployment inside the city is more than 10%. (The suburbs around Detroit, meanwhile, are growing.) If trends hold, Detroit will be altered beyond recognition by 2100.
As Detroit flirts with demographic disaster, some cities face the natural kind. Researchers at the University of California, Davis, forecast a 75% chance that San Francisco will be struck by a major earthquake of magnitude 7 or above by 2086. Some might argue that city dwellers will survive and rebuild, although the fate of New Orleans in the wake of Hurricane Katrina, which flooded 80% of the city in 2005, offers mixed lessons.
San Francisco is also one of the fastest-shrinking cities in California, part of an overall population shift away from the expensive and geographically hazardous coast toward inland cities. A major disaster could accelerate that trend."