Interesting article.

http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2004/12/16/BAGK4ACKAP1.DTL

Furlong pointed to indirect evidence for the Marin fault during an interview Wednesday -- the unusual steepness of water-carved ravines along ridges toward the southern end of Marin County. The ravines grow steeper and steeper toward the southeastern end of the hills and ridges that dominate the Marin County terrain, according to Kirby's analysis of geological records.