Calif. falls behind on mapping quake fault lines
By Rong-Gong Lin II, Rosanna Xia and Doug Smith, Los Angeles Times
After the 1971 Sylmar earthquake, California began to map faults across the state.
Over the next two decades, officials published 534 maps of active earthquake faults. New construction was prohibited on top of these fissures because previous quakes showed that buildings could be torn apart during violent shaking.
But the mapping campaign has slowed to a crawl – with many dangerous faults still undocumented.
Since 1991, only 23 have been drawn. Because of budget cuts, none were completed between 2004 and 2011.
State officials said there are still about 300 maps to draw and even more to revise – including some in heavily populated areas of Southern California. That represents about 2,000 miles of faults statewide.
The slow pace affects public safety. The ban on building atop faults is enforced only for those mapped by the state; the regulations don’t cover faults not on California’s official map.
Officials are also concerned about several other zones they believe need further seismic research, including San Diego Harbor, Yorba Linda, the San Gabriel and Pomona valleys, Indio, Napa County and South Lake Tahoe.
