The costliest quake in U.S. history hid on a fault no one had mapped — a 'blind thrust' that never reaches the surface. It cracked steel-framed towers thought immune.
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DownloadThe Northridge earthquake struck at 4:31 a.m. on January 17, 1994, on a previously unknown blind thrust fault buried beneath the San Fernando Valley. Because the fault never reaches the surface, it had left no obvious trace — a reminder that some of Los Angeles's most dangerous faults are the ones no one can see.
Although it was only magnitude 6.7, it produced some of the strongest ground accelerations ever recorded in an urban area. Freeway overpasses collapsed, apartment buildings pancaked, and losses ran into the tens of billions of dollars — among the costliest natural disasters in U.S. history.
Dozens of people were killed and thousands injured. The quake reshaped California's building codes, especially the rules for steel-frame buildings and elevated freeways.