1^90 



s. SEKIYA AND F. ÔMOKI. 



the Univei'sitv. whicli was specially desigDed for recording strong 

 eartliquakes. The instrument is in principle the same as those often 

 described in the papers in the enrlier numbers of this Journal treating 

 of seismological subjects. The main differences are, ((/) the working 

 ])arts are made stoutei' to withstand severe shakings, (h) llie writing 

 }>ointers are made longer so as to record large ranges of motion, and 

 (r) the p(jinters have no nudti[)licati<)n ratio so that the actual magni- 

 Uidc of the motion is givcü. This !-< the first time that a clear 

 instrumental reconl of a destructive earthfpiake was evei- taken in 

 this count rv : ]»r(jbal.)ly no such has ever been obtained in any other 

 countr}'. 



The Seismograph records the motion decomposed into three 

 components. The wave lines on the two inner circles indicate one 

 tlie XE-ISW, and the other the SE-XW components, and that on 

 the outermost circle the vertical component. By compounding the 

 (•om|ionent motions we can und the resultant. The recording plate 

 revolved once in ILS seconds, and the short radial lines mark succes- 

 sive seconds of time counted from the start. AVe can thus determine 

 the mtiunitude and direction (^f motion at anv instant during the 

 earthquake, as well as the durarion. the intensity, and other elements 

 of the shock. ]>elo\v we give results deduced ïvoui the diagram. 



Time of üccüiTcncc. lSi)4, June l^Otli, '!'■ V" W p.m. 



Jlori'jonlal Moliott. The earth(pial-:e began as usual with tremors. 

 The duration of tremors, as indicated liy ordinary seismographs, lasted 

 about 10 seconils. The Lar^e ^Motion Seismograph dc^es not record 

 minute tremors, and the motion w;is already a few millimetres in 

 rarjue at the beij-inninu' of this diai>-ram. Howe\er. we shall take this 

 latter point as the beginning of the eartlujuake. The motion, already 

 strong in the Lst and '2nd seconds, became suddenly violent and 

 the ground moved o7 jnm. durinir the time interval Ijetween the ord 



