172 SOUTHERN CALIFORNIA GEOLOGY 



NORTHERN SECTION OF THE SAN ANDREAS 



RIFT 



The writer claims no great personal familiarity with 

 the northern section of the San Andreas Rift, although 

 his experiences with it have been as many as some of 

 those who write about Southern California over- 

 confidently. Its features have been rather fully de- 

 scribed in the geologic literature and worked out in 

 great detail in places. Its general occurrence is shown 

 on the maps of the Earthquake Commission and the 

 Earthquake Map of the Seismological Society. These 

 details will be seen to differ greatly from those of the 

 Southern Segment. 



The southern part of the Northern Section is merely 

 the easternmost member of a wide belt of rifts which 

 I have termed the Coast Range Belt of structures. 

 Going northward its course first follows the elongated 

 Carrizo Plain. North of the latter it becomes asso- 

 ciate with a narrow zone of parallel faults which pass 

 by or near San Lorenzo, Lobo, San Benito, and Hollis- 

 ter. The elongated Salinas Valley lies to the west of 

 its path. 



The San Andreas Fault line proper passes eight miles 

 southwest of the center of San Francisco as one of 

 a narrow belt of similar rifts which extend from the 

 sea border as far east as Berkeley, the whole constitut- 

 ing a narrow, faulted zone of more or less active seis- 

 micity according to the Fault Map of the Seismological 

 Society. 



THE SOUTHERN SECTION 



The Southern Section of the San Andreas Rift be- 

 gins at the bend several miles south of Maricopa and 

 follows a course of south 56° east for two hundred 



