422 EEPORT— 1888. 



Eighth Report of the CoviTnittee, consisting of Mr. R. Etheridge, 

 Mr. Thomas Gray, aoid Professor John Milne (Secretary), 

 appointed for the purpose of investigating the Earthquake and 

 Volcanic Phenomena of Japan. (Dratvn up by the Secretary.') 



Earthquakes in 1886. 



In my fourth report to the British Association (1884) I gave the results 

 obtained from the observation of 387 earthquakes which had occurred 

 between October 1881 and October 1883 in North Japan. The vahiable 

 nature of these results led the Meteorological Department of this country 

 to establish post-card stations throughout the empire, with tbe object 

 of making similar but move extended observations. An epitome of the 

 results obtained during 1885 was given in my sixth report to the British 

 Association, and through the kindness of Mr. Aria Ikunosake, the Director 

 of tbe Meteorological Department, I am now enabled to give a summary 

 of the observations made in 1886. Here and there these are supple- 

 mented with my own remarks. 



(a) Frequency of EarthquaJces. — During 1886 the number of earth- 

 quakes recorded in Japan was 472, which is equivalent to an average of 

 13 per day. In 1885 there were 482. Tbe greatest number of shakings 

 felt in any one province was in Shimotsake, 30 or 40 miles north of 

 Tokio, where sixty-one shakings wore recorded. Some of the provinces 

 on the western side of the empire do not appear to have felt any 

 shakings. 



(h) Distribidion of Seismic Energy. — Speaking generally, the eastern 

 part of Japan was greatly shaken, while to the west of the mountains, 

 forming the backbone of the country, disturbances were rare. The 

 general distribution of seismic energy therefore remains as it bas been in 

 previous years. If, however, we make a detailed examination of this 

 distribution, a few exceptions to the observations of 1885 may be dis- 

 covered, one of which was the great increase in the earthquakes felt in 

 Shinano, an inland province 60 miles east of Tokio, and the other in the 

 province of Echigo, about 100 miles north of Tokio. In Shinano the 

 number of shocks increased from 9 to 19, while in Echigo they increased 

 from 3 to 31. In other provinces a decrease was observed. 



It is extremely interesting to observe that Echigo and Shinano lie 

 along a N.N.W. line, which, so far as the strike of rocks is concerned, 

 divides the main island of Japan into two halves. Along this line, and to 

 the noi'th and east of it, there are many volcanoes, while to the west and 

 south there ai*e practically none. The strongest shock was the Echigo- 

 Shinano shock of July 25, which cau-ed considerable damage to build- 

 ings, walls, bridges, &c. 



The districts most shaken were the east coast from Tokio northwards, 

 the north-east corner of Yezo, the southern extremity of the Kii peninsula, 

 and the southern part of Kinshin. 



The positions of the origins of the shocks which have been recoi'ded 

 were approximately as follows : — 



