The Hayward Fault is a major geological fault located in California, running approximately 74 miles through the East Bay region. It is part of the larger San Andreas Fault system and is known for its potential to produce significant earthquakes. The fault has a history of seismic activity, with the last major earthquake occurring in 1868. This fault poses a risk to nearby cities, including Oakland and Berkeley, due to its proximity to densely populated areas. Scientists closely monitor the Hayward Fault to better understand its behavior and to improve earthquake preparedness in the region.