The Hayward Fault
 joint project with Math Science Nucleus, City of Fremont, U.S. Geological Survey, California Geological Survery


The Science Behind the Fault
Major Fault Lines in California

The map shows several fault lines that exist in California. The Pacific Plate is moving north relative to the North American Plate, creating the San Andreas Fault System, which also includes the Hayward Fault. This is also called a Transform Boundary, as the plates slip and slide pass each other.

North of Cape Mendicino the slip/slide motion changes to converging.  The Pacific Plate is being subducted under the North American Plate causing volcanoes as well as earthquakes.  Transform motion only has earthquakes.

In the San Francisco Bay area the Hayward Fault is one of three major fault zones  (including the San Andreas and Calaveras) of the San Andreas Fault System that has produced large historic earthquakes


There are many earthquake faults in the San Francisco Bay Area. A fault is a break in the Earth’s crust, caused by movement of rigid blocks. The Hayward Fault dissects Fremont creating offset features. The In 1836 there was a large earthquake but the larges was felt on October 21, 1868. 

The Hayward Fault is an offset of the San Andreas Fault system that dominates the landforms of eastern San Francisco Bay.  The relative motion between the North American Plate  (southeast) and the Pacific Plate  (northwest) create stress that releases energy as earthquakes. This slip slide motion is called a transform fault.  The Hayward Fault is within the San Andreas Fault  Boundary Zone between the North American Plate and the Pacific Plate.  The Hayward fault is one of only a few dozen faults in the world that “creeps,” or slowly moves.  Evidence of creep can be found from Pt. Pinole in the north to south Fremont.


The Hayward Fault has a strike-slip motion which is when one land mass moves, nearly horizontally in the opposite direction of the other on the surface. This movement causes stress, which results in earthquakes. The Hayward Fault is a strike-slip fault on the surface but changes to a low angle thrust fault as it descends under the Easy Bay Hills. This creates an uplift of the East Bay hills in the Fremont area exposing the rocks of the Briones Formation, which is a fossilerous rock made of marine shells.  It is Miocene in age and can be correlated to other similar sediments throughout coastal California.


In the big picture, scientists know where the fault is because of curbs and streets being offset from fault creep, pre-development aerial photos showing creeks shifted and other markers of fault movement, and from previous trench exposures showing the fault below ground.   Scientists can take sonar pictures of the earth below.




strike slip fault motion Hayward Fault going under the East Bay Hills in Fremont area


What is a fault creep?

  • Fault creep is the slow, almost constant movement along a fault without large earthquakes. Creep is unusual. 
  • Most faults around the world only slip during earthquakes generally larger than magnitude 6.7.  The Hayward Fault slips both during those large earthquakes and also the rest of the time from fault creep.
  • The Hayward Fault in Fremont creeps about 3/16ths of an inch (5mm) per year.  The fault needs to move about 6/16ths of an inch (9mm) per year to release the energy building up at the surface.
  • Fault creep is only happening in the upper couple of miles of the fault's total 8 mile depth, at least for most of the length of the fault. The lower part of the fault is locked and has to release energy during bigger earthquakes.

 What happened in the last big earthquake on the Hayward fault?

  •  The last big earthquake along the Hayward Fault was in 1868.  It was approximately a magnitude 6.9.
  • The fault broke for about 30 miles from around Milpitas to the Oakland-Berkeley border.  The fault slipped 3 to 6 feet along the fault.  The western side moved north and the eastern side moved south.
  • At the exhibit, the fault slid about 3 feet.  It was closer to San Leandro where the fault slipped about 6 feet.  This is what is likely to happen in the next big quake along the Hayward Fault.



MATH SCIENCE NUCLEUS since 1982 has served the education and public by offering quality science and math lessons that take our children learn critical thinking skills. We manage the Children's Natural History Museum and Tule Ponds at Tyson Lagoon Wetland Center.

CITY OF FREMONT is located in the southeast San Francisco Bay area and straddling both the East Bay and South Bay regions.  It has a population of close to 1/4 million people and one of the largest city by land in San Francisco Bay area.   
U.S. GEOLOGICAL SURVEY is a government agency that Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment.  They provide the posters and map for the Faulted Floor Exhibit.
CALIFORNIA GEOLOGICAL SURVEY was established in 1860, and one of the oldest geological surveys in the United States, serving as a primary source of geologic information for California’s government agencies, businesses, and public.


Math/Science Nucleus
 4074 Eggers Drive, Fremont, California, U.S.A., 94536
 (510) 790-6284

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