Hayward Fault

The Hayward fault extends from San Jose 120 km or about 74 miles northward along the base of the East Bay Hills to San Pablo Bay. Two types of fault movement occur along faults. One type is the catastrophic rupture of the ground that generates large earthquakes. A large earthquake, estimated to have been about magnitude 7, occurred on the Hayward fault in 1868 and was the "great" earthquake of the Bay Area prior to 1906. Descriptions from the 1868 Hayward earthquake report a meter or about 3 feet of fault rupture in the City of Hayward. The other type is a very slow movement of the fault, a few millimeters or a fraction of an inch a year that does not generate earthquakes. This slow movement, called fault creep (or tectonic creep) can easily be observed where cultural features such as streets, curbs, and buildings straddle the Hayward fault and are deformed by the slow movement. Fault creep is most easily recognized where curbs and other structures are bent in a specific direction called right-lateral offset. Right lateral describes the horizontal movement of one side of the Hayward fault relative to the other side of the fault. This can be observed when you sight down along the curband the curb is bent to your right. These right-lateral offsets or bends produced by creep line up street after street, identifying the precise location of the Hayward fault

The above is the hayward fault seen in a large pit dug 15 feet into the ground in the central park of Fremont.
Number of people witnessed the fault on this day, the 29th of April 2006.
Clear evidence of fault creep is found in Fremont where Gardenia Way crosses the Hayward fault near Ivy. A sequence of fractures or shears forms diagonally across the asphalt pavement in the street.
The close-up of the fractures in the asphalt on Gardenia Way. These are an excellent example of left-stepping en echelon shears, where the next set of fractures is to the left of the last set. These result from right-lateral slip on the Hayward fault.


The Hayward fault can be identified in several locations crossing the streets in Fremont. Note the bend and break in the curbs at Rocket Drive.