EARTHQUAKES 



277 



This earthquake was the result of shocks produced by renewed 

 slipping along an old fault line which had been known to geologists 

 for some time. The " earthquake topography " of such a fault line 



124° 123° 



122° 



« 



/ ' 



-300 miles / 



.WEvn-eka 



'As 



Cape |/ V 

 Mendocino |N ^"*\ 



\ U 



KPetrolia ^^ 



1 ) 





V^ ^e* 



7 o> 



M 



-250 Vv. ti 



\ \ \ 

 \ \ J, ' 



— \Pt.Delgada\ ;> 



\ l\ \ 







\ Sv \ 



< ^ 





1 t^ \ \ 



V 





\-k * S Y? 







-ZOO \ lO) / O 















x \\ 







\\ ° rx 



\j» 





0> \l Utaah £\ 



>^ -39 



39 



- X ^i^ 





Point Arena VA-^ ^j 











-'SO ^ N^* 







Yk** 







vT 



Sacramento V 





^\ FartRoss^. 







N \ Santa Rosa J 





TomaZesBay \^ 







-100 <-^ hn-ernes^A 





3d 



"f^?^ *^2^- ^s -38 





Bolinas^^-\ 



J> VOBerkeley <a \ 

 -® VOaWand ■* \ 





SAN FRANCISCO^ 





Mussel Rock 







O 



\ \fe- 





-50 



\~ San Jose' 





O 



\ \ 



2" 



X*> 



-0 -^> 

 1 I 



Santa Criz \ \ HolKsteT 

 \ X ° 



VrMonterey 

 .1 > 





12*° 123° 



122° 



Fig. 275. — Map of the fault line formed during the San Francisco earthquake in 

 1906. It was the vibrations set up by the faulting along this line that produced the 

 earthquake. (U. S. Geol. Surv.) 



is described on page 265. The fault line along which the slipping 

 occurred has been traced about three hundred miles on the land 

 (Fig. 275), and the principal movement was found to be horizontal 



