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Putting the great quake in context

April 18, 2006

The 1906 San Francisco earthquake began just off the Golden Gate at 5:12 a.m. By 5:16, 290 miles of the 750-mile San Andreas fault had ruptured. The quake caused a devastating fire and released incredible energy, about 16 times more than the Loma Prieta earthquake, which took place during the 1989 World Series. Research of other large quakes shows that the most severely damaged structures are found within 3.1 miles of the ruptured fault. Here is a look at the famous fault.

Plate tectonics and the San Andreas

The San Andreas fault is essentially the intersection of two massive tectonic plates that are grinding against each other, building tension that can be released violently when portions of the plates suddenly slide forward.

40 million years ago: Ancient Farallon plate is subducted slowly beneath North American plate.

20 million years ago: Farallon plate nearly disappears; Pacific and North American plates collide.

Today: Pacific and North American plates push in opposite directions along


Sources: U.S. Census Bureau, California Geological Survey, U.S. Geological Survey, Assn. of Bay Area Governments, "A Land in Motion: California's San Andreas Fault." Graphics reporting by Julie Sheer, Les Dunseith

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