210 



REPORT — 1898. 



Niigata, and Nemuro. This would lie about 150 miles east of Sendai, 

 at a depth of 4,000 fathoms, exactly at the bottom of the Nippon slope of 

 the Tuscarora Deep. This is practically the same origin as that given for 

 the shock of June 15, 1896,' as it is for many other disturbances which 

 have shaken the whole of the Japanese islands. Facts to be noticed about 

 this particular group of earthquakes are that they are the largest, that 

 they originate along the base of the steepest slope, and that it is only 

 occasionally that they are accompanied by sea waves. The disturbance of 

 June 15, 1896, was accompanied by waves which resulted in the loss of 

 nearly 30,000 lives, whilst the shaking of the ground was barely percep- 

 tible at Tokio. The earthquake about which I now write as a producer of 

 earth waves which could be felt was much more marked than that of 

 June 15, and yet sea waves were not recorded. The inference is that the 

 earthquake of August 5 was not accompanied by any marked displace- 

 ment of large bodies of material at the bottom of the ocean, and its origin 

 was practically beneath the sub-oceanic crust. It is therefore possible 

 that we have in the Tuscarora earthquakes examples of disturbances due 

 to accelerations in the secular flow of a quasi-rigid subterranean material 

 under the influence of continental load. If this is the case we should 

 expect to find records of local magnetic perturbation. 



Velocity of Propagation of Barth, Waves. 



Assuming the origin of the earthquake to have been 250 geographical 

 miles to the north-east of Tokio, and the wave to have been propagated 

 to that place at a rate of about 8,000 feet per second, then the time at 

 "which the earthquake originated in G.M.T. was August 5, 9 mins. 23 sees. 



G.M. T. — Times at which Freliminary Tremors commenced in Europe. 



(Large waves ?) 63 



M. S. 



13 12 

 23 17 

 15 12 

 37 

 7 



Apparent Velocity of Preliminary Tremors. 



Shide . 

 Italy about . 

 Tokio . 



No. 120, August 16, 1897. 



n. M. s. 



8 6 29 



8 15 at Catania, Ischia, Rome, Eocca di Papa. 



7 53 33 Duration 3 mins. Slow movement. 



' Also see British Association Report, 1896, p. 153. 



