260 



Y. OINOUYE 



I. EARTHQUAKES AND ROARINGS 



Preceding the eruption there were frequent earthquakes, seem- 

 ing to repeat the past history of the mountain, which has always 

 exhibited the "foreshocks" in advance of an eruption. But the 

 writer believes that the occurrence of so many earthquakes in the 

 neighborhood of a volcano within the limits of Japan is a rare 

 phenomenon. It was rumored that slight earth movements were 



Fig. 2. — A fissure on the road near Abuta 



noticed six days before the eruption. But, as observed by a few 

 persons, the first earthquake began on the evening of July 21, four 

 days in advance of the eruption, and successive earth tremblings 

 were felt from the morning of July 22, continuing through the 

 eruption and for two months thereafter. Numbers of these 

 quakes were felt at Nishimombetsu, 8.4 km. southeast of Usu, 

 25 on July 22, no on July 23, 354 on July 24, 163 on July 25, and 

 thereafter in gradually decreasing numbers. It was on the evening 

 of July 25 that the first eruption took place, and, after it had relieved 

 the strains to some extent, the quakes began to decrease in number. 



