The San Andreas Fault is like the Sword of Damocles dangling over California, a constant reminder of catastrophe waiting in the wings. In a state so prone to a wide range of disasters that they seem routine, the thousand-mile-long San Andreas Fault remains the single largest threat. This fault flattened and burned much of San Francisco in 1906; it ruptured for hundreds of miles and severely rocked the land for nearly three minutes in 1857 (when Los Angeles was a little town along a river); and it’s responsible for the 11,000-foot mountain ranges that account for the wind, rain, and fire conditions that cause other forms of disaster.
Nowhere is the danger of impending catastrophe more palpable than in Southern California, where the southernmost segment of the San Andreas Fault has gone more than 300 years without breaking. This segment ruptures every 150 years on average, so it’s long overdue for a very large quake. In the parlance of one seismologist, the San Andreas Fault “is 18 months pregnant.”
What effect will a 300-mile-long, 30-foot rupture of the San Andreas Fault in California have on 20 million people, the buildings they live in, and the ground their cities are built on? It’s long been understood that such a quake would be devastating, but that wasn’t enough for post-9/11 and post-Katrina catastrophe planning measures in the United States. To get a better handle on the seismic effects and resultant potential consequences of such an event, the U.S. Geological Survey (USGS), two years ago, commissioned the most detailed study ever of the San Andreas Fault.
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