ON THE EARTHQUAKE PHENOMENA OF JAPAN. 201 



of motion at these different stations intersect each other in a number of 

 points between Yokohama and Kanasawa. 



Although several other earthquakes have had their origin localised in 

 the same district, there remain several, the origin of which has not been 

 localised, the records of direction being probably in many cases, and 

 certainly in some, a confusion of normal and transverse vibrations. 



As a confirmation of these results, I find by a careful series of time 

 observations made by myself in Tokio and in Yokohama, by Mr. W. H. 

 Talbot, for the accuracy of which we are indebted to the telegraph 

 department who daily furnished us with a time-signal, that many shocks 

 have been felt about 30 seconds in the latter place before they were felt 

 in the former. 



The facts that in Yokohama small earthquakes are sometimes felt 

 which are not recorded in Tokio, and also that at the time of a severe 

 shock the vertical motion appears to be greater in Yokohama than in 

 Tokio, may also be taken as indications that the origin of many of the 

 recent earthquakes has been nearer to Yokohama than to Tokio. 



In order to make the localisation of the various shocks more certain, 

 I have very recently established instruments in Tokio and Yokohama 

 which give graphical records of both the normal and transverse vibrations. 

 When similar instruments have been established at the remaining stations, 

 the complete distinction between these two sets of vibrations may, inde- 

 pendently of the interest that these records have of themselves, assist us 

 to determine the origin of nearly all the earthquakes we feel. 



The district where several shocks have had their origin already 

 localised is one showing numerous faults, and one which shows exceed- 

 ingly clear evidence of recent elevations. As it is very possible that this 

 district may still be rising, one probable inference we might make is that 

 faults are still being formed, and are due to the elevations, and that 

 the earthquakes are to us the announcement of the formation of these 

 fractures. 



As confirmatory of this idea we may say that, first, the records of 

 earthquakes, as written by our seismographs, usually commence gently, 

 then have several maxima and minima, and finally die out as they com- 

 menced ; and secondly, the testimony of our feelings leads us to believe 

 that there is a sliding, jolting kind of motion, as might be produced by one 

 mass of rock slipping over another. 



Further, I may remark that recently, since having more perfect in- 

 struments which record each successive vibration of the earth, both in 

 regard to time and space, I have recorded shocks in Tokio with a motion 

 almost entirely east and west, whilst the time observations showed that 

 they must have come from the south, which is the faulted district. 



Assuming that these records are correct, and I have no reason to 

 believe that they are not so, it would seem that from the faulted district 

 in the south it is possible to receive an earthquake consisting only of 

 transverse vibrations. 



Such an earthquake we can imagine might be produced by a fault 

 giving rise to an elastic wave of distortion. 



If the earthquakes were produced by a blow we should have a wave 

 of compression with normal vibrations, followed by a wave of distortion, 

 with transverse vibrations. 



Observations bearing on these points I hope to carry out during the 

 coming year. 



