CATALOGUE OF EARTHQUAKES 



1918—1924 



Seismology owes a very great debt to the British Association, which has in this 

 instance, as in many others, taken an infant science under its fostering care. Under 

 the guidance of John Milne a world-wide organisation was started for the use of the 

 seismograph when it was a new instrument, and lists of earthquakes (epicentres and 

 times) were pubUshed in the Seismology Reports to the British Association up to the 

 time of Milne's death in 1913. Other organisations were started, especially the 

 splendid Russian network of observatories under Galitzin, and the International 

 Seismological Association which had its headquarters at Strassburg ; but the one 

 started by MUne and fostered by the British Association was the only one which 

 survived the war ; though the Russian network has now been revivified, and a new 

 international organisation has since 1922 had its headquarters at Strasbourg in place 

 of the one which died with the change of name . Meantime the lists of earthquakes 

 disappeared from the Reports to the British Association, being replaced first of all 

 by lists in the Shide Bulletins which gave not only the epicentres and times as before, 

 but comparisons of the observations with adopted tables. Ultimately the pubUca- 

 tion of these collated lists was taken over by the Seismology Section of the Inter- 

 national Union of Geodesy and Geophysics, and became the International Seismological 

 Summary, of which the annual volumes for seven years (1918-1924)have already been 

 published, each year in four quarterly parts. 



2. These Summaries are distributed to all the contributing observatories and to 

 various libraries, but do not reach a very wide non-seismological public. It seems 

 possible that there is such a public (reached, for instance, by the British Association) 

 which might be interested to have, apart from the technical details, a simple list of 

 all earthquakes which occur, with their epicentres and times, such as Milne used to 

 give ; though it is easy to give to-day more information than was possible in the 

 early years of instrumental seismology. Accordingly the following catalogue has 

 been prepared from the International Seismological Summary. 



3. The first columns give the date of the shock in Greenwich time, the next the 

 latitude (North -f. South — ) and longitude (East-f , West—). Then follows a column 

 showing the number of stations which have given recognisable observations of the 

 shock, thus indicating very roughly which are severe shocks observed at considerable 

 distances, and which are only slight and local. But this indication is subject to a 

 serious systematic error. It is clear that a shock in Europe, for instance, even though 

 slight, may be observed at a number of stations, which cluster round it, while a much 

 severer shock in the Antarctic might escape notice altogether. It would be better 

 to attempt some indication which is independent of the distribution of observing 

 btations ; but this would need a special research for which no time has hitherto been 

 available. The work of preparing the Summary has already strained such resources 

 as are available for it. However the Summary itself provides an indication of another 

 kind. Those shocks for which the preliminary wave P has been observed at a distance 

 of at least 80° from the epicentre are undoubtedly in a different class from other 

 earthquakes. The same could not be said of observations of the long waves L, or 



1928 » 



