PRELIMINARY TREMOR OF EARTHQUAKE MOTION. 



149 



By examining the seismographic diagrams of different 

 earthquakes, it will be seen that in general the duration of the 

 preliminary tremor is longer for distant earthquakes than for 

 those of near origins. Its duration in some typical earthquakes, 

 as recorded in the diagrams, I shall now proceed to consider. 



2. Observations at the Meteorological Observatory of Gifu 

 (lat. 35°27^ long. 136°460. The observations at Gifu of the 

 great Mino-Owari earthquake of tlie 28tli October, 1891, and 

 of five of its strongest after-shocks are given in the following 

 table : — 



Earthquakes observed at Gifu. 



Of these 6 earthquakes, No. 1 was caused by the forma- 

 tion of a long fault, most remarkably shown in the Néo- 

 Valley, whose central part is about 30 kilometres distant from 

 Gifu. The remaining five earthquakes all originated in the 

 Mino-Owari plain, not far from the same city. 



3. Observations at the Meteorological Observatory of Kago- 

 shima (lat. 31°35/, long. 130°330. 



The observations at Kagoshima of the violent earthquake 

 of the 7th September, 1893, and two of its after-shocks were 

 as follows : — • 



