California is home to hundreds of faults. This partly explains why the state sees so many earthquakes. They can range wildly in size and shape.
A fault is a fracture zone between two large blocks of rock. Some, like the San Andreas Fault, are hundreds of miles long, traverse most of the state, and remain active to this day.
There are three main types of faults: normal, reverse (or thrust), and strike-slip faults. All are responsible for earthquakes, but the majority of the faults here in California are strike-slip faults.