228 SOUTHERN CALIFORNIA GEOLOGY 



San Andreas, Santa Ynez and San Jacinto Rifts. The 

 City of Los Angeles is also at a sufficiently safe dis- 

 tance from the immediate seaboard and the great 

 abysmal escarpment of the continental shelf to give us 

 reasonable assurance against shocks from sea-marginal 

 slipping. 



Even though a master shock should take place along 

 the south end of the San Andreas line of seismicity in 

 Southern California there is no reason for asserting 

 that Los Angeles would be seriously affected by it 

 inasmuch as that fault does not come closer than 

 thirty miles of the city. The average distance of Los 

 Angeles from the path of this fault across Southern 

 California is far greater than that amount. In other 

 words, Los Angeles is sufficiently remote from this 

 dangerous line of seismicity and horizontal movement 

 to discredit the belief that the city is apt to suffer 

 serious damage from it. 



The Pacific side of California is but a small part 

 of a greater Pacific border-line of seismicity many 

 thousands of miles in length whose trace is some- 

 times in the ocean and sometimes on the land, and it is 

 utterly impossible to predict where the greatest strains 

 are along its length or where and when the next great 

 shock or release will occur. Inasmuch as Southern 

 California occupies but a fractional part of this greater 

 line of seismicity, it likewise follows that the theory 

 of alterations of severe seismic occurrence between 

 Northern and Southern California, as advanced by Dr. 

 Willis, has no foundation. 



This theory of alternations has been disproved by 

 the fact that three great releases have taken place in 

 the north in the latter part of 1927 since the predic- 



