142 F. OMORi : 



9 -|- minutes. The average period of vibration in the preliminary 

 tremor, whose duration was about 22 seconds, was 3.7 seconds. 

 The average period of vibration in the principal portion was 7.2 

 seconds, the maximum range of motion being 0.15 mm. in each 

 component. Towards the end, the average period was 3.7 seconds. 



24. The earthquake of the 12th August, 1898 ; 8.38.33 a.m. 

 The total duration of this earthquake, whose origin was 



approximately in the same locality as in the preceding case was 

 about 30 minutes. The average period of vibration in the preli- 

 minary tremor, whose duration was 122 seconds, was 3.7 seconds. 

 Then followed 15 larger undulations of the average period of 3.7 

 seconds, the maximum range of motion being in the EW com- 

 ponent 0.2 mm. and in the NS 0.1 mm. The average period of 

 the next 30 vibrations was 7 seconds, the maximum range of 

 motion being in the EW component 0.4 mm. and in the NS 0.2 

 mm. Towards the end, the average period of 60 vibrations was 

 7 seconds, and that of the next 60 vibrations 8.1 seconds. The 

 diagrams are given in tigs. 20 and 21. 



25. The earthquake of the 7th October, 1898; 11.1.1a.m. 

 This earthquake, which shook, with varying force, the 



northern part of the Main Island and the southern part of 

 Hokkaido, had its origin in the Pacific, off the eastern coast 

 of the Province of Rikuoku, about 640 km. NE by N of 

 Tokyo. The total duration was about 30 minutes, while the 

 duration of the preliminary tremor was 82 seconds. The average 

 period of the prevailing slow undulations in the principal portion 

 was 6.0 seconds, the maximum range of motion being in the 

 EW component 0.3 mm. and in the NS 0.45 mm. The average 

 period later on varied between 3.9 and 6.1 seconds, becoming 

 longer towards the end. 



