282 T. Tekaua and T. Matuzawa 



will be the most precious data for seismologists and geophj^sicists. 

 Horizontal displacements of triangulation points were also measured 

 in the Sakurazin)a eruption and the great Kwanto Earthquake. In the 

 latter case, the points observed are sufficiently numerous, so that an 

 analytical study seems possible for the determination of the precise 

 mode of deformation of the surface in this region. Equal merit must 

 be acknowledged for the work of the Hydrographic Office^^^ of the 

 Imperial Japanese Navy by which the remarkable upheaval and 

 depression in the sea bed of Sagami Bay after the recent great earth- 

 quake were brought to light. The phenomena revealed are quite 

 unique in the history of earthquakes. Various interpretations have 

 been proposed as to the nature of the change observed. T. Muramoto^^^ 

 and T. Ogawa"^"^ attribute the change to the sliding of the submarine 

 deposit aloDg the slopes of the sea-bed, while T. Terada^"*^ quotes 

 Wegener's hypothesis regarding the different natures of the crust under 

 land and sea and suggests the possibility of a remarkable plastic 

 deformation of the sea-bed near the disturbed sial mass. 



A Similar work of sounding was carried out on the occasion of 

 the recent Tazima Earthquake. ^^^ No remarkable change in the sea- 

 bed was ascertained in this case. 



Connected with the above, a fact of considerable significance was 

 reported by H. Nagaoka,'^^^ Saem. Nakamura,^"^ K. Suda^^^ and others, 

 that for several years preceding the great earthquake, the region which 

 underwent upheaval by the earthquake, had been experiencing a 

 gradual depression. Suda'^^ compares this case with that of the 

 rebound observed in the case of the San Francisco Earthquake of 1906 ; 

 while Terada^'"^ proposed a simple mechanical model for explanation. 

 Imamura,^^^^ however, remarks, from his examination of mareograms 



(1) T. Uchida, Ho., lOOB (1925). A special Eeport (1924) issued by Hydr. Oflf. 

 Soundings of shallow waters have also been carried out by the authorities of the Fishery 



Institute of Tokyo ; the results were published in a pamphlet. 



(2) A pamphlet issued by the Hydrographical OfSce. 



(3) Chikyu, 1 (1924), 405; Jap. J. Geo]. Geogr., 3 No. 3-4(1924), 1. 



(4) Ho., lOOB (1925). 



(5) A pamphlet issued by the Hydr. Off. 



(6) Syoka-manroku, (1924), 124. 



(7) Eeport on the Kwanto Earthquake (1924), Centr. Met. Obs. 



(8) U. t. S., 3 (1923), 177. 



(9) Mem. Imp. Mar. Obs. 1, No. 4 (1924). 



(10) Ho., lOOB (1925). 



(11) Ho., lOOB (1925). 



