1857 Fort Tejon earthquake

Fifty one years before the Great San Fransisco Earthquake (Mag 7.7 - 7.8), there was the Fort Tejon quake, Mag ~7.9. It ruptured the San Andreas Fault for a length of about 225 miles (350 kilometers), between Parkfield and San Bernardino.

en.wikipedia.org...

From Science 10 July 2009:
Vol. 325. no. 5937, pp. 191 - 193

Nonvolcanic Tremor Evolution and the San Simeon and Parkfield, California, Earthquakes
Robert M. Nadeau and Aurélie Guilhem

Nonvolcanic tremors occur adjacent to locked faults and may be closely related to the generation of earthquakes. Monitoring of the San Andreas Fault in the Parkfield, California, region revealed that after two strong earthquakes, tremor activity increased in a nearly dormant tremor zone, increased and became periodic in a previously active zone, and has remained elevated and periodic for over 4 years.
...

The persistent changes in tremor suggest that stress is now accumulating more rapidly beneath this part of the San Andreas Fault, which ruptured in the moment magnitude 7.8 Ft. Tejon earthquake of 1857.

[edit on 17-9-2009 by RoofMonkey]