Hi Todd. Large quakes don’t occur at the surface. They occur at depth where there is sufficient material to lock the fault.

Surface fault ruptures come in all shapes and sizes but do not occur with every earthquake. They only happen when the quake is of sufficient size and is shallow enough whereby the fault rupture can break the surface.

The lowest magnitude earthquake to create surface fault ruptures is about a mid to upper M5 event. The focal depth must be shallow and on the order of less than 10 km and more like 2-6 km.

Generally speaking, the larger the earthquake, the larger the potential surface fault rupture. Shallow earthquakes registering about M6.0 produce surface fault ruptures on the order of 2 feet and quakes of M8.0 or greater generate ruptures on the order of 30-50 feet.

Each earthquake has its own specific characteristics, which govern its rupture behavior. Whether horizontal or vertical, or a combination of both, surface fault ruptures are spectacular.

Here in the Hollister area we can see the results of fault movement in our streets, sidewalks and homes. Of course we don’t see it with a large quake, but with the continuous movement of the Calaveras Fault, which is about 7mm per year at most locations. Take Care…Don in creepy, but sometimes shaky town

• Hollister