160 A. Imamura 



standard beiicli-iuark at tlie ground of tlie Military Staff did not 

 undergo any change, but it is likely that it suffered a depression of 

 about 50 mm., if the level shown at the tidegauge station of Abura- 

 tubo be taken as the standard. 



Early in 1925, the survey was repeated along two lines, one from 

 Tokyo to Aburatubo and the other from Hudisawa to Atami. The 

 result is that the places which had shown upheaval in the previous 

 observation, indicated a slight depression not greater than 6 cm., so 

 that there is evidence of the recovery of the land from topographical 

 changes caused by the earthquake. This phenomenon is said to have 

 been very conspicuous in the most elevated localities shortly after the 

 catastrophe. 



Now let us add a few words about the results of land siu'veying 

 in the central part of the province of Sagarai. By accurate obser- 

 vations made soon after the earthquake, it w^as found that one of the 

 base lines, about 5 km. in length and with the approximate orienta- 

 tion of north to south, increased in length as much as 24.5 cm. and 

 raised its south end higher than the other by 14.7 cm. This obser- 

 vation corresponds with the result of the lienchmark survey. 



16. Change of the sea-bottom. In comparison with the upheaval 

 of the land, quite startling is the change of the sea-bottom in Sagami 

 Bay, which was discovered by elaborate work on the part of the 

 Imperial Naval Hydrogi-aphy Department. The result is shown in PI. 

 XV, in which only the elevations and depressions exceeding 30 m. are 

 represented, those less than that amount being omitted. It is estimated 

 that the area and volume of depression amount to 700 sq. km. and 

 50 en. km. respectively, and those of elevation to 240 sq. km. and 

 20 cu. km. in all. This result was obtained after soundings had been 

 carried out at 83,286 points distributed in the area between Tyosi in 

 the east and Suruga Bay in the west, and between Tokyo Bay in the 

 north and the Miyake Island in the south, and comparisons made 

 with the results of the former soundings carried on mostly during the 

 year 1912, corrections due to the tides of the different periods and 

 meteorological disturbances being, of course, taken into account. The 

 results seem at a glance to be extravagant, but nevertheless it is highly 

 probable that they do not deviate so much from the actual state, 

 though it is slightly doubtful whether the change took place wholly 

 on the present occasion. Thus we may conclude that the following 



