140 



Transactions. 



The waves used for determining the origins are the preliminary tremors 

 and the long waves ; the methods for the most part trial methods, such 

 as the differential method and that based upon the interval between the 

 arrival of the P x waves 

 and those of maximum 

 amplitude. 



The results for eleven 

 earthquake s in which the 

 data are sufficient to 

 determine the epicentra 

 are given below. Those 

 called "approximate" 

 are epicentra probably 

 correct within the limits 

 of error of the observa- 

 tions ; those called 

 "probable" are epicentra 

 for which there are re- 

 sidual errors somewhat 

 in excess of the limits of 

 errors of observation. 



(It should be noted 

 that the method of least 

 squares cannot properly 

 be used unless the phy- 

 sical conditions are ap- 

 proximately the same. 

 For instance, we cannot 

 use it in reference to 

 equations based upon ob- 

 servations from stations 

 varying greatly in their 

 distance from the origin ; it should be applied only to deductions from 

 observations of waves passing along the same paths, or, assuming the 

 symmetrical distribution of the various strata of the earth, passing along 

 paths of nearly the same length.) 



The origin in each case may, of course, have been a more or less exten- 

 sive mass below the epicentrum indicated on the map (fig. 1). The map 

 also shows the positions of previously ascertained origins in Australasia. 



Remarks. 



Not recorded in Europe or other 



distant .stations. 

 Recorded at near and distant sta- 



Fig. 1. 



Earthquake-origins in the South-west Pacific, 1910. 



I G. Hogben.j 



• Approximate epicentrum. 



O Probable epicentrum. 



x Origins previously found. 



tions. 

 Ditto. 



Between Campbell Islands and An 



tipodes islands. AH stations. 

 All stations. 



