EARTHQUAKE 



2766 



EARTHQUAKE 



Earthquake. Examples ot damage wrougiu D> modern eartuquaKes. 1. ta^v.ue 01 Messina Cathedral before tbe earth* 

 quake ol 1908. Z. As it appeared afterwards. 3. Capitals of columns displaced at Leland Stanford Jr. University, Cal iornia, 

 1906. C. CatnedraJ destroyed in Guatemala City, 1918. 5. Wrecked railway bridge ^ear Gifu, Hondo, Japan. 6. Ruined 

 street in Giiu. 7. Intenor of tbe church of Calcmaja. near Pisa, destroyed in Sept., 192C. 8. Street rent asunder in San 

 Francesco 1906. 9. Collapsed tower at Santa Rosa, California, 1906 



from Italy to Burma Count de 

 Montessus de Ballore tabulated the 

 records of over 170,000 earth- 

 quakes, and found that all but 

 5 p.c. occurred near these two 

 mountainous axes. 



Seismology owes much to Japan- 

 ese interest ; during seven years, 

 1885-92, over 8,000 shocks were 

 recorded in Japan, most of them 

 happily of small dimensions ; yet 

 in 1891 a severe shock left exposed 

 a new escarpment which extended 

 50 m. and attained a height of 20 ft. 

 The San Francisco earthquake 

 was marked by a vertical displace- 

 ment which in places amounted to 

 10 ft. and which extended for over 

 250m. Usually the shock lasts for a 

 little longer than a minute ; the am- 

 plitude of the vibration diminishes 

 with distance from the origin. 



The seismograph, or earthquake 

 recorder, is a solid pillar set up 

 solidly in the ground at a distance 

 from all chance causes of surface 

 vibrations in the earth, and so 

 arranged that every vibration in 

 the earth's crust is communicated 

 through the pillar to a recording 

 pen. From the automatic records 

 of three stations the seismologist 

 determines the time, character, and 

 place of origin of the earthquake. 



In Britain occasional earth- 

 quakes cause little damage beyond 

 the breakage of ornaments thrown 

 from their shelves and of pictures 

 detached from their hooks ; but in 

 areas liable to these disturbances 

 the landscape may be permanently 

 altered by the formation of scarps 

 and landslips, rly. lines and fences 

 may be broken and displaced side 



ways, buildings may become heaps 

 of rubble. Great waves may be 

 generated in the ocean. 



In earthquake areas great atten- 

 tion must be paid to the stability 

 of buildings ; they should be low 

 upon a broad foundation, so that 

 the swaying roof does not move 

 far beyond the outside limits of 

 the foundations. It used to be 

 thought that the typically light 

 bamboo house of the Japanese was 

 developed in consequence of the 

 frequency of earthquakes, but the 

 thick, heavy, solid roofs of these 

 houses show that the lightness of 

 the walls is not due to tear ot 

 earthquakes. If Japanese domestic 

 architecture owes any' of its 

 characteristic features to the fre- 

 quent earth-waves, it is in the shape 

 and lowness of the buildings 



