148 



A. IstAMUEA 



The data shown in the table furnish a good illustration of the 

 relation between the time of the con)inencem(^nt of the earthquake 

 and the focal distance. The time curve thus obtained is i^racticall}' 

 a straignt line given by the equation y = 7 6x — 10, where y repre- 

 sents the focal distance in km. and x the time in seconds. It gives 

 lib 58ni 32s as the time of commencement at the origin, and 

 7.5 km. /sec. as the transit velocity of the elastic wave in the vicinity 

 of the origin. 



The direction of the initial phase is very important first, in the 

 determination of the seismic origin, and secondly in conjecturing the 

 cliaracter of the seismic action. For the former, the observations at 

 Mera, Numadu, Kohu and Tokyo are most im[)(n-tant, especially the 

 last in consequence of its having given the most accurate result ; and 

 now I find that the coordinates of the origin already given do not 

 require any correction. In regard to the character of the seismic action, 

 it is to be reniarked that within a radius of 170 km. there exist four 

 different sectors : namely, the first including Numadu, Mera and Tyosi, 

 the second including Tokyo, the third including Ivumagai and Maebasi, 

 the fourth including Kohu. Of these, ol)Servations at stations in the 



