The Calaveras Fault is a right-lateral strike-slip fault about 120 kilometres long in the San Francisco Bay Area, branching off the San Andreas near Hollister and running north through the East Bay past San Jose and toward Danville. It is one of the principal splinters of the San Andreas system and takes up a meaningful share of the plate-boundary motion east of the main fault.
The fault is famous among geologists for its creep: along its central section near Hollister the ground slips steadily without large earthquakes, slowly offsetting curbs, walls and buildings in the town. This aseismic creep releases some strain gradually, but the northern segment is locked and stores energy for larger, sudden ruptures.
The Calaveras has generated several damaging quakes, including the 1979 Coyote Lake earthquake (magnitude 5.7) and the 1984 Morgan Hill earthquake (magnitude 6.2). Studies suggest the northern Calaveras could join with the Hayward Fault to produce a much larger event affecting the densely populated East Bay.