DE I EL OP ME NT OF SEISMOL OGY IN JAPA N 30/ 



seismic stvuctures may especially he mentioned. More recently, N. 

 MononoLe*^^ ■ made a wide sm'vey on this prohlem, discussing the forced 

 vihrations of the most varied structm-al elements, the extension heing 

 made to examples with yielding supports. K. Suj'ehiro^^^ also contri- 

 buted some papers which treat of the vibrations of chimneys and other 

 structures, to a degree of approximation higher than hitherto resorted 

 to. He drew attention to the existence and its significance of the 

 rocking vibrations of a building as a whole. He'"'- also devised 

 with the aid of M. Isimoto an apparatus consisting of an elongated 

 U-tube filled with mercury, by means of which he was able to study 

 closely the vibrations of a building in its different parts simultaneously 

 with those of the underlying earth's surface. A somewhat similar 

 apparatus was constructed by J. Obata^^- which enables us to register 

 extremely minute vibrations by means of an electric micrometer of his 

 own design. 



Omori*^-^^ made a widely extended study on the natural periods of 

 different kinds of buildings, towers, chimneys and those large build- 

 ings recently constructed in the central quarter of the metropolis. 

 He utilized this method of measurement as a means of diagnosing the 

 strength of buildings against earthquakes. To cite an example, the 

 Marunouchi Building is said to owe its comparative immunity in the 

 last great earthquake to the remedy applied after the former earth- 

 quake of the 26 April, 1922, according to the result of his diagnosis. 



Imamura is now carrying out an investigation on the vibrations 

 of the iron frame work of the Parliament building under construction, 

 by registering sitnultaneously the motions of the different stages due 

 to earthquakes. A remarkable occurrence of resonance has been ascei-- 

 tained. 



The various investigations of Omori and others"^^^ on the vibrations 

 of chimneys or towers have also brought forth many interesting results, 



(1) Dotoknkwaisi, 5, No. 3 (1919); 6, No. 4 (1920). See also his paper on the 

 destructive pawer of earthquakes, Jap. J. Astr. Geopliys., 3 (1925), 7. 



(2) Kead befoi-e a Meetin<» of the Math. Plivs. Soc. Jap. ; not yet published. 



(3) K. Suyehiro and M. Isimoto, N.S.B.K., [iii] 7 (1925), 85. 



(4) Not published ; the electric micrometer is described in the Keport of tlie 

 Aeronautical Research Institute, Imp. Univ. Tokyo, I (1925) 305. 



(5) Ho., 29 (1899); 97A (19211; Pub., 12 (1903); 20 (1905); Bull., 9, No. 1 

 (1918); No. 3 (1921^ 



(6) Omori, Ho., 28 (1895); Pub., 12 (1903). Tanakadato and Mano, Ho., 21 

 (1898). Mano ;ind Tanabe, Pub., 3 (1900), 



