The Carrizo Plain Natural Area is one of the most desolate and stark landscapes in California. It is located in a valley west of Bakersfield and east of San Luis Obispo, out of the way of most traffic patterns and with nearly zero population. Devoid of much vegetation except grass, the golden hills of the Carrizo Plain feature the most clearly visible evidence of the San Andreas fault anywhere in California. From the air, the fault looks like a gash cut across the surface of the earth. From the ground, offset creeks and sag ponds offer tangible evidence that you are no doubt located in the "belly of the beast". At Wallace Creek, geologist Charles Rubin from Central Washington University is planning a new trench where he'll be able to interpret the language of the earth's layers to determine a pre-written human history of earthquakes in this area. This type of research is called paleoseismology. Often, the goal of paleoseismology is to be able to predict a seismically-active region's recurrence interval; that is, about how much time passes between major earthquakes in that area. The most common and successful technique used by modern paleoseismologists is trenching—the digging of trenches in strategic locations of earthquake-prone areas. The soil and rock revealed can show evidence of prior earthquakes, such as rock layers that are shifted or displaced. By carefully measuring and dating such features, scientists can learn when and where earthquakes have occurred, how big they were, and with what frequency they strike. More than just a matter of academic interest, this information can be crucial in deciding whether an area is safe to build on.
The shadow of a scarp betrays the path of the San Andreas fault.
Wallace Creek is split in half, or "offset", by the San Andreas fault, which runs right through its stream bed.

On the Road with the Faultline Project
©1999 Exploratorium