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Tour of the Hayward
Fault
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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. |
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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.
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