San Francisco: Living on borrowed time?

More than 40 people died after the two-level Cypress Street Viaduct of Interstate 880 in Oakland collapsed during the 1989 earthquake. Although the structure had been retrofitted 12 years earlier - the viaduct was built on what had been marshland - it collapsed after soil liquefaction occurred.

The San Francisco bay area sits along major fault lines and thus runs the risk of suffering devastating consequences should it ever get hit by a monster-sized earthquake. But the problem isn't necessarily that earthquakes are increasing in frequency or size. In fact, says Colin Stark, Lamont Associate Research Professor at the Lamont-Doherty Earth Observatory of Columbia University, the problem is that we prefer to keep believing the dice will fall in our favor and so we keep building. "Megacities across the world continue to grow, and many are along major faults. Most of these faults have not generated giant earthquakes in recent memory, but historical and geological records, supported by abundant geophysical data, show they do so every few hundred years," he wrote in an op-ed piece for CNN.com.

Credit: Wikipedia