The Hayward Fault is a right-lateral strike-slip fault. A right-lateral strike-slip fault has a vertical fracture and each side moves to the right, so that a person facing the fault would see objects on the other side moving to the right of his current position.
The Hayward Fault is about 45 miles long and runs through the densely populated San Francisco Bay area. The fault was responsible for an earthquake in 1868 that killed at least 30 people. Geologists estimate that the fault causes an earthquake between every 140 to 170 years. The two other types of faults are called "normal" faults and "thrust" faults.