On the After-shocks of Earthquakes. 



by 



F. Ömori, Rièakushi. 



I. General Considerations. 



§ 1. A strong' earth(|uake is almost invariaMy followed by 

 weaker ones and wlien it is violent and destnictive the nnniljer of 

 minor shocks following it may amonnt to Imndreds or even thousands. 

 When after-shocks are not reported to have happened it is probably 

 because they were deemed unimportant to record. Or it may be tliat 

 the seat of origin of the earth([uake being very deep or fir out under 

 the ocean-bed, the after-shocks did not reach the observer. 



Complete records of after-shocks were obtained, I believe, f )r the 

 first time in the cases of the three recent great earthquakes in Japan; 

 namaly, those of Kuinimoto in 1889, of Mino and Owari in 1891, 

 and of Kagdshimi in 1893. The discussion of these records forms 

 the subject of the present paper. 



§ 2. The numbers, daily, monthly, etc., of the after-shocks of 

 these three earthquakes, together with other matters relating thereto 

 are contained in Tables I — XXII at the end of the paper ; the shocks 

 being distinguished as " violent," " strong," and '" weak " (or " feeble ") 

 according t<3 their intensity ; the total or aggregate intensity of a 

 number of shocks is ol)tained by multiplying each shock by one of the 

 coefficients 3, 2, 1, according to its intensity, and taking the sum of 

 the numbers so obtained. Tlie after-shocks of the Mino-Owari earth- 



