Bureau of Land Management, California.
Here you are standing on the San Andreas Fault. At this location it runs northwest to southeast a the base of the hills. At one time Wallace Creek drained straight across the fault, but movement by the San Andreas Fault has offset its drainage course, with the downstream segment about 430 feet northwest of the upsteam segement. This is one of the best examples of stream offset across a fault in the world. An interpretive trail is available to learn more about this portion of the San Andreas Fault.
Once on Carrizo Plain National Monument, continue on Soda Lake Road to Simmler Road. Turn on Simmler Road. Take Simmler Road to Elkhorn Road and turn right. Continue on Elkhorn Road for about 1 mile. Parking lot for Wallace Creek will be on your left. **NOTE** Simmler Road is impassable in wet weather.