158 A. Imamitra 



and 46 liours to consume 71^ or the maximum. Many whirlwinds 

 were also experienced in Yokohama and Odawara. 



13. Intensity distribution in Yokohama. Variety in seismic in- 

 tensity was also observed in the city of Yokohama. In the lower 

 parts of the town, the intensity is likely to have attained two-fifths 

 of gravity in the case of recently-made ground like Isezakityo, and 

 one-third of gravity in districts of rather old formation like Hontyo- 

 dori, while the intensity was only one-sixth to one quarter of giavity 

 in diluvial ground on the hills. The severe damage in the case of 

 the softer ground may also be due to the irregular subsidence of the 

 gi'ound (PL XXXIX, XL.). 



14. Differences in intensity due to geological formation The 



fact that the seismic intensity was moderate (about one-tenth of gravity) 

 in the area covered by tertiary formation or solid volcanic rock in the 

 peninsulas of Boso, Miura and Idu, notwithstanding their having been 

 very near the origin of the quake, may be understood from a con- 

 sideration of the nature of the rocks and of their resistance to the 

 seismic waves as shown in the results of observations at two different 

 seismic stations in Kamakura. PL XX. B shows the relation between 

 the ratio of intensity in the alluvial ground and that in ground of 

 tertiary formation, as well as the period of corresponding earth move- 

 ments in the latter place. Special relations are likely to exist between 

 them in the case when the period is less than 8 sec, but for the 

 present purpose, it will be sufHcient to consider only cases in which 

 the period is 1-2 sec, as such a period is common in destructive 

 earthquake motion, thus showing an increase of seismic intensity of 

 four or five times that of harder ground. 



15. Change of landscape. Thousands of conspicuous land slides 

 took place in the Miiu-a and Idu Peninsulas, the southern part of the Boso 

 Peninsula and the njountainous district of south-western Sagami, the 

 most fearful having been the mud-flow which buried the whole village 

 of Xebukawa with its 700 inhabitants in the southwestern part of 

 the jjrovince of Sagami. The area along which this mud-flow swept 

 down is a narrow ravine about 6 km. long and 150 m. wide with 

 an average slope of 1/9 (PL XXL). Avalanches of soil and rock, 

 which had been disintegrated from three or four spots in the eastern 

 flank of the somma of the Hakone Volcano, united on their way to 



