Post 3.  Look northeast (upstream).  Follow the course of the small creek down to the fault where you are standing.  Now look southwest (downstream), and see if you can find it.  You might not see it at first.  Where did the channel go?

From Post 3, walk northwest 30 feet (9 m) along the fault.  Look again for the downstream channel.  It is not as obvious as the upstream channel, but it is still a visible gully.  Like Wallace Creek, this channel has been offset by motion along the San Andreas fault.

Now do the same at Post 4.  If you can find the offset channel, you are doing the work of a geologist!