Frequently Asked Questions
Okay, so now I know where the San Andreas fault is. But there is a much more impressive mountain front -- the base of the Temblor Range -- just to the northeast. What is that?
There are faults at the base of the Temblor Range, but they are separate from the San Andreas fault. The Temblor Range is being pushed up by faults on both sides of the range and in the middle. These faults are blind thrust faults, meaning that they are thrust faults which do not come to the ground surface. It is not clear to geologists how the thrust faults connect to or relate to the San Andreas fault at depth.
The thrust faults are much smaller than the San Andreas. As you have learned, the San Andreas is slipping at a rate of 34 mm (1.3 inches) per year.&nbps; By comparison, the thrust faults are probably slipping at a rate of no more than 1 mm (0.04 inches) per year. The reason the Temblor Range may appear more impressive than the offsets along the San Andreas fault is that, at the base of the Temblor Range, the motion along the faults is vertical. Vertical relief is much easier to see than horizontal displacement.
What about the western side of the Carrizo Plain? Are there any faults there?
The Caliente Range, along the western margin of the Carrizo Plain, is full of faults and folds, but most of them are no longer active. The only active faults that reach the surface are at the southern end of the Caliente Range, near Cuyama Valley. The range is noticeably embayed -- it does not have a sharp range front like the Temblor Range -- which suggests it has not been tectonically active for a considerable period of time. You can learn more about the Caliente Range in the Carrizo Plain Geologic Tour guide.
The U.S. Geological Survey has compiled a comprehensive list of frequently asked questions related to earthquakes and faults. Please explore the USGS Earthquake FAQ page for answers to additional questions.