what is the major fault in California where the San Franciso earthquake occurred?
Feb 20, 2010
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Earthquake Questions
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3 comments
Zach on February 20, 2010 at 6:17 pm
San Andreas Fault
crazykim on February 20, 2010 at 6:17 pm
The San Andreas fault
It is a transform fault boundary, and can actually be seen above ground unlike other faults.
Mark V on February 20, 2010 at 6:17 pm
The 1903 San Francisco earthquake occurred along 296 miles of the San Andreas Fault. As there was no proper technology at the time, the magnitude can only be rather guessed at. Accepted values are between 7.7 and 8.25 moment magnitude.
The other major 20th century earthquake, the 1989 Loma Prieta earthquake, was a 6.9 moment magnitude (7.0 on Richter scale) that also caused by slip along the San Andreas Fault.
The San Andreas is the transform boundary between the Pacific and North American plates, and is thus a place of great tectonic stress. It has many smaller branch, or tributary faults that are also dangerous. For instance, the 1994 Northridge earthquake had a moment magnitude of 6.7, but its actual ground motion, property damage, and death toll was significant. It did not take place along the San Andreas, but on a previously unknown thrust fault. There are many known and named tributary faults all through California, running 800 miles from the Sea of Cortez to north of the Bay area, at which point it veers west into the Pacific.