Although the San Andreas Fault is more commonly known, the Hayward Fault by Fremont, California is capable of causing destructive earthquakes. Hayward Fault Zone is roughly 37 miles in length and is generally along the western hills on the east side of San Francisco Bay. This fault line runs through the areas of El Cerrito, Richmond, San Leandro, Hayward, Berkeley, Fremont, Oakland and San Jose. The Hayward Fault line is parallel to the San Andreas Fault and in conjunction with the Calaveras Fault which is east of the Hayward Fault has helped produce severe earthquakes.
There is a trench across the Hayward Fault which is aptly named the Hayward Fault Exposed. This trench opened in 2006 and is open to the public for viewing on Saturdays and Sundays. Docents are on hand to explain what people are seeing as well as for safety. The fault is 40 miles in length and has a depth of 8 miles. The trench on the east side is composed of 9,000 year old silt and the opposite side was also part of Alameda Creek's silt, yet it is only 4,000 years old. To date there are no fossils in this trench; however, other trenches nearby have produced horse teeth, a 4,000 year old human bone and mastodon bones.