THE GREAT EARTHQUAKE OF S. E. JAPA.V 153 



is only 2 3 km. 



In the Boso Peniusula, the saucly dishict around Hodyo showed 

 a maximum intensity almost equal to that in the district of the same 

 geological nature at Kamakura. Here the phenomena of displacement 

 were observable in a few simple houses, but the amount did not 

 exceed 30 cm. The direction of the principal earth-movements seems 

 to have been SE-NW for the most part in the peninsula. (PL XXXIII) 



Another interesting phenomenon was observed on the ground of a 

 primary school at Hodyo. Here two parallel fissures each having a 

 length of about 22 metres were formed ; they opened and closed 

 alternately several times, intermittently euntting turbid water as high 

 as three meters. This geyser-like phenomenon was witnessed by the 

 school-master and teachers, who estimated the period of eruptions to 

 have been about 10 seconds. When I visited the place two months 

 later, traces of the mud- vol canoes and of the fissures which had ex- 

 tended in the north-southerly direction were still recognizable. The 

 site of the school had formerly been part of a paddy field, but was 

 changed into the present state a few years ago, dry soil having been 

 laid at the place as high as 60 cm. above the original level. The 

 paddy field covers an area elongated from north to south and is 

 enclosed by comparatively hard ground from which the school ground 

 now projects towards the east like a peninsula in the semi-liquid 

 field. In such places, gravity waves of stationary character are liable 

 to occur, so that phenomena similar to those described above may be 

 produced at places corresponding to the loop of the undulation. The 

 large fissures which are recorded to have swallowed men and cattle in 

 the cases of the great earthquakes of Lisbon in 1755 and of Jamaica 

 in 1692 may possibly be due to similar causes, though Japan has 

 never experienced such awful cases. 



11. Earthquake phenomena in Tokyo. The ground of the city 

 of Tokyo also shows differences in seismic intensity. Previously I 

 have drawn a map showing the distribution of intensity areas in Tokyo, 

 taking into account the results ex[)erienced in the cases of the de- 

 structive earthquake in. 1855 and the semi-destructive one in 1894, 

 the geological structure, the history of the formation of certain parts 

 as residential land and the seismographic study of four different places 

 in or near the city. Soon after the last catastrophe, I took up this 

 problem again, and began to study the phenomena not only in the 



