SCIENTIFIC BACKGROUND 171 



cated by the topography of the northeast sides of Cata- 

 lina and San Clemente Islands. 



MORE ABOUT THE SAN ANDREAS RIFT 



The San Andreas Rift as an entirety, has been previ- 

 ously discussed as a portion of the boundary of the San 

 Bernardino Plateau, in our brief description of the San 

 Gorgonio Pass and under the headings of the "Line of 

 Greatest Seismicity." Likewise, we have referred to 

 the previous and more detailed writings on the subject 

 by Fairbanks, Noble and others. 



The California portion of the line is divisible into 

 two distinct sections each with different directions and 

 details of occurrence. The portion of the northernmost 

 of these in California, which I herein call the Northern 

 Segment, is some three hundred and fifty miles long. 

 It extends from Cape Mendocino to a point near the 

 thirty-fifth parallel of latitude in the southwest corner 

 of Kern County, about ten miles south of Maricopa, 

 and near the junction of the counties of Kern, San 

 Luis, Santa Barbara, and Ventura. This segment has 

 a trend of north 40° west and is a member of the Coast 

 Range belt of fault lines of similar direction which 

 parallels the coast of California to the north and which 

 has as yet no defined analogy in Southern California. 

 (See Plate III.) 



In so far as the geographic relations of the two sec- 

 tions are concerned, both may be considered as accom- 

 paniments of the structural features which I have 

 herein termed the Coast Range Belt and the San 

 Andreas-Puente Belts respectively, along which the 

 rift breaks up into branches as I have shown on Plates 

 II and III. 



