20 SOUTHERN CALIFORNIA GEOLOGY 



marine line which has extended southeasterly along the 

 west coast of North America from the Arctic Circle. 



Its continuations southeastward, known as the San 

 Andreas and San Jacinto rifts in Southern California, 

 do not stop at the Mexican border, but extend far 

 onward into the Mexican and tropical regions, where 

 they are present, although the details of their occur- 

 rences there are still unstudied. The international 

 boundary is not a physiographic one, as is the great 

 Transverse Structural Belt which separates Southern 

 from Northern California, but these fault lines con- 

 tinue indefinitely beyond it. 



SEISMICITY OF SOUTHERN CALIFORNIA 



Records of the shakes and tremors which have taken 

 place in Southern California have been made until quite 

 recently without system or scientific supervision, and 

 usually with exaggerated details. In fact, few accurate 

 facts about the quakes of the last century have been 

 preserved. 



The knowledge of this subject has suffered from the 

 erroneous policy of concealment of facts at home and 

 from criminally exaggerated reports in the eastern 

 papers. Eastern papers of August, 1927, contain vivid 

 but untrue accounts of ''tall buildings dangerously 

 swaying" in Los Angeles at the time of a slight shake 

 early in that month. 



Careful research has been made by others to ascer- 

 tain the earthquake history of California, and their 

 results have been published in the scientific journals. 

 The work along this line has been especially painstak- 

 ing and instructive. The results may be found in 

 various numbers of the Bulletin of the Seismologic 

 Society of America, particularly the number for June- 



