Vol. 65.] OF THE CALIFORNIA^ EARTHQUAKE OF 1906. 15 



The San Francisco earthquake of 1906 is being subjected to an 

 investigation more complete and exhaustive than any great earth- 

 quake has yet received ; the report, when completed, will be a 

 document of the greatest importance, and, until it lays all the 

 details before us, any attempt to follow up the subject would 

 be futile : yet this much is evident, that the great fault was not 

 the sole, nor even the principal, cause of the earthquake, and that 

 the movement along it was merely an incident in the final rupture, 

 consequent on the growth of a widespread strain, distributed over 

 an area of the earth's crust comparable in magnitude with, and 

 possibly equalling or exceeding in size, the seismic area. This 

 strain was of the nature of a shear, such as might be produced by a 

 shifting more or less parallel with the coast-line, with compression 

 in a direction about north and south and extension in a direction 

 about east and west. How it was produced cannot be established, 

 and more than one hypothesis is tenable ; but, however produced, 

 one thing is clear, that the forces concerned must have been very 

 different from those which led to the formation of the San Andreas 

 fault. The earthquake, therefore, cannot be regarded as an incident 

 in the growth of the fault, nor the fault as the cause of the 

 earthquake. 



Appendix. 



List op Displacements associated with the Califarnian earthquakes of 1868 

 and 1906, as determined by the U.S. Coast $ Geodetic Survey in 1906-07. 



Position 



relative 



to Fault. 



Mount Toro 



Gavilan 



Point Pinos Station 



Point Pinos Lighthouse . 

 Santa Cruz Lighthouse . . 

 Santa Cruz Az. Station. . 



LomaPrieta 



Lick Observatory 



Black Mou ntain 



Pulgas E. Base 



Sierra Morena 



Red Hill 



Pulgas W. Base 



Cruano Island 



Montara Mountain Peak 



Flat 



San Pedro rock 



False Cattle Hill 



Road 



San Bruno Mountain ... 



nn. 



20 

 4-0 



24 



24 



12 



12 

 3-0 



22 

 09 

 7-0 

 2-7 



12 

 2-2 

 6-0 

 3-8 

 0-9 

 4-6 

 2o 

 0-9 



Displacements 



1868. 



1906. 



ft. i dir. 



99 S.53°E. 



2-1 N.52°E. 



2 



Combined. 



dir. ft, 



N. 12° W. 



117-1 



161 



1193 



N.37°WJ ... 



S. 57° E. 13-1 

 E. 



N. 44° W. 

 N. 35° E. 



1-3 



N. 34°E. 

 N. 24° W. 

 N. 11° W. 

 N.29°W. 

 N. 28° W. 

 E. 7°S. i 



S. 51° E. 

 S. 33° E. 

 S. 37° E. 



S. 15° E. 

 S. 54° E. 



S. 44° E. 

 S. 58° E. 



N. 47° E. 

 S. 16° E. 

 S. 28° W. 



