EARTHQUAKE MEASUREMENT AT MIYAKO. 173 



14. Eqke. No. 10. The 27th March, 1897 ; 7.46.43 p. m. 

 Intensity, slight. The origin was situated probably at about 70 

 km. NE of Miyako. (See %. 7). 



The motion, which consisted of regular ripples, was larger 

 in the (EW) than in the (NS). The duration of the H.M. was 

 80 seconds, and that of the V.M. was 47 seconds. 



The preliminary tremor, whose duration was 4.2 seconds, 

 consisted in each component of vibrations of an average period 

 of 0.078 second. 



The transition from the preliminary tremor to the 2)7'i)icipal 

 portion of the shock was marked by the aj)pearance of slow 

 undulations with minute ripples superposed, which formed the 

 apparent continuation of those in the preliminary tremor, but 

 whose period became slightly longer than before. The average 

 period of the ripples in the principal portion, whose duration 

 was about 24 seconds, was 0.100 second in the (EW), 0.093 

 second in the (NS), and 0.091 second in the (V); the maximum 

 range of these vibrations being 0.39 mm. in the horizontal, and 

 0.08 mm. in the vertical component. 



From about 29 seconds after the beginning, the period of 

 ripples became again shorter, being practically the same as that 

 in the preliminary tremor, namely, 0.076 second in the (EW). 



The elements of the slow undulations were as follows : — 



15. Eqke. No. 11. The 30th April, 1897; 5.51.15, a.m. 

 Intensity, weah. This was a small local sliock, whose origin was 

 situated probably at about 60 km. NE of Miyako. (See fig. 6). 



