260 T. Tekada and T. Matuzawa 



referring directly to the position of the origins instead of taking the 

 districts disturbed. 



Eecently T. Terada^^^ nieutioned a peculiar fact that the distribu- 

 tion of the two groups of districts which show opposite relations with 

 regard to the correlation between the yearly fluctuation of atmospheric 

 pressure on the one hand, and a factor determining the distribution 

 of faculae on the solar disc on the other, is quite similar to the 

 distribution of the two Groups above cited. On the other hand, T. 

 Tokuda^^^has remarked a striking difference in the geotectonic structnre 

 of the Pacific and of the Japan Sea coast, the block structure and. 

 the folded structure being respectively conspicuous in the tertiary 

 formations of the two zones. These latter facts, though apparently 

 quite separate from each other, may suggest some connection with 

 Omori's result here cited. 



(b) Diurnal variation. The diurnal variation has also been 

 studied most extensively by Omori^''^^ who found that the frequency of 

 earthquake is closely related to the variation of the barometric pres- 

 sure. For the most districts, the maximum of pressure corresponds to 

 the maximum of the frequency. 



(c) Lunar variation. The periodic variation of frequency related 

 to lunar day or tidal level has also been investigated by Omori^'^^ 

 Though the lunar effect is much complicated, it has been inferred 

 that the frequency is enhanced in the epochs of the upper and lower 

 quadratures. The results have been explained by the effect of the 

 oceanic tides 



Honda'-"^^, in his investigation of the level change of wells, remarked 

 some relation between the frequency of eartliquakes and tidal 

 phases. 



On the other hand, Imamura^''^ studied the synodic-monthly dis- 

 tribution of the frequency. The results obtained are rather complicated. 

 Four maxima or two were found for the earthquakes of submarine 

 and of inland origin. The results have been explained by the inter- 

 ference of the effects due to the barometric and tidal pressure. 



(1) Journ. Coll. Sci. Tok., 44, Art. C. (1923). 



(2) Geogr. Eev., No. 10 (1925L 



(3) Ho., 2 (1894); 30 (1900). 



(4) Ho., 32 (1900); 54 (1906); Bull., 5, No. 2 (1913) 



(5) Pub., 18 (1904). 



(6) Ho., 18 (1904) ; T.B.S.K., 2 (1904,\ 109. 



