Tour of the Hayward Fault

 

Introduction to the 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 curb and 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.

Tour of the Hayward Fault from Fremont to San Pablo Bay

This photographic tour will follow the Hayward fault, picturing some of the most easily recognized surface features, from the City of Fremont toward the southern end of the fault, northward to Point Pinole on the margin of San Pablo Bay.

Copyright Dr. Sue Ellen Hirschfeld

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