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The Great Shake: San Francisco 1906
page 5 of 10, Exploratorium


The Richter ScaleIt was, of course, an earthquake, THE earthquake, one of the largest ever to hit North America, and the first of 27 separate quakes that day. The first shock -- at 5:12:05 a.m. -- lasted more than 40 seconds. It was by far the largest, estimated to have been 8.3 on the Richter scale; its epicenter was just off the coast, around Pacifica.

How big was it? Two of the world's largest tectonic plates, the North American and the Pacific, had lurched past each other at a distance of between nine and 21 feet along the San Andreas fault. The temblor shook the ground and left a wake of destruction 290 miles long -- from Mendocino to Monterey Counties -- with shock waves that traveled at over 7000 miles per hour.

Church  
Click here for a larger image of the church.

In the city of San Francisco, it toppled chimneys and smokestacks, crumpled wood-frame houses into kindling, threw walls into the streets, and twisted steel rails and cast-iron ducts as if they were pipe cleaners. All the churchbells in the city were set to clanging, as if signaling doomsday, the end of the world.


was not in use
in 1906. Seismologists used the Rossi-Forel scale, which measured earthquakes on a scale of 1 to 10. The 1906 quake was classified as a No. 9, an earthquake that throws down badly built buildings and gives the streets of the city a large amount of debris. It is as about as severe an earthquake as can be experienced without total destruction, without great yawning chasms and complete destruction of life and property."


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Life Along the Faultline © 1999, The Exploratorium
 

Photo credit: Seismograph Record from the Steinbrugge Collection, Earthquake Engineering Research Center, University of California, Berkeley