On a series of previously unknown faults that lies parallel to the San Andreas.
About 120 miles from San Jose.
The big question is, where did the strain shift to?
Map of the quakes, with nearby faults:
[link|http://quake.usgs.gov/recenteqs/FaultMaps/121-36.htm|http://quake.usgs.go...ltMaps/121-36.htm]