NOTES ON JAPANESE EARTHQUAKES. 427 



27. Secular variation of seismic activity in Kyoto. Tables 

 XXI and XXII give respectively the yearly numbers of earth- 

 quakes in Kyoto for the two most disturbed epochs, namely, the 

 9th century and the time interval between 1340 and 1609, the 

 total activity for each year being the sum of the numbers of 

 small, strong and destructive earthquakes multiplied respectively 

 with the coefficents 1, 2 and 2. The results contained in these 

 two tables are illustrated in figs. 16 and 17, from which it will 

 be seen that the seismic activity presents a series of fluctuations of 

 periods varying between a few years and a few dozen years. 

 The curve for the 9th century indicates more or less definitely 

 a period of the average length of 62 years. In figs. 16 and 17, 

 each of the small circles (o) on the abscissa axis indicates a 

 destructive earthquake in Kyoto, and it may be observed that 

 about the year 1360 small earthquakes were very frequent in 

 Kyoto, but these w^ere accompanied by no destructive shock. 



