1909.] OUTLOOK OF SEISMIC GEOLOGY. 265 



It must be regarded as quite remarkable that the recognition of 

 this fundamental fact was reached in Austria, for the opportunities 

 offered by the Austrian field were by no means exceptional. In 

 fact, the great surface faults which have been a feature of great 

 earthquakes in other districts, have there been seldom observed. 

 In New Zealand, for example, accompanying a heavy earthquake in 

 1856, an area of country comprising 4,600 square miles was sud- 

 denly upraised to form a visible escarpment varying from one to 

 nine feet in height. This event was duly described by Lyell, who, 

 in the eleventh edition of his widely read "Principles of Geology" 

 reported this and other similar cases apparently without seeing that 

 they throw any discredit upon the centrum theory. 



In 1884^ Gilbert, in a brief note, explained the earthquakes char- 

 acteristic of the Great Basin of the western United States as due 

 to the interrupted jolting uplift of the mass of the mountains by 

 vertical thrust. The stresses tending to uplift the range aided by a 

 fissure already in existence, accumulate until they overbalance the 

 starting friction upon the fissure, when through movement the strain 

 is relieved and the potential energy of the system reduced. In a 

 later note published in 1890^ he showed that during the earthquake 

 of 1872 in the Owen's Valley, California, the ground was moved in 

 strips both vertically and horizontally. 



In 1893 Koto, describing the great Japanese earthquake of 1891, 



in referring to earlier earthquake rents within the same district 



said: 



The event of October, 1891, seems to me to have been a renewed move- 

 ment upon one of these preexisting fissures — the Neo Valley line of fault, 

 by which the entire region lying to the right of it not only moved actually 

 downwards but was also shifted horizontally towards the north-west for 

 from one to two metres along the plane of dislocation. This vertical move- 

 ment and horizontal shifting seem to me to have been the sole cause of the 

 late catastrophe.* 



Without the aid of surface faults, Leonhard and Volz, in 1896, 

 expressed clearly the idea that the Silician earthquake of 1895 was 

 the result of an adjustment among orographic blocks or Schollen. 

 Their statement was : 



^ Amer. Jour. Sci., Vol. 27, 1884, pp. 49-53- 

 ='Mon. I., U. S. Geol. Sur., pp. 360-362. 

 ^Jour. Coll. Sci., Tokyo, Vol. V, 1893, P- 329- 



