230 



DK. CHAELES DAVISON ON THE 



[May 1904, 



towards the north-west, and intersect the surface along a line 

 passing near, or a short distance to the south-east of Hognaston. 

 The epicentre, or the chief part of it, evidently lies hetween the 

 two epicentres of the principal earthquake (of March 24th) ; while 

 the displacement towards the east or south-east of the isoseismal lines 

 with respect to those of the principal shock shows that, if connected 

 with the same fault, the focus must have been situated much nearer 

 to the surface. The latter inference is also supported by the 

 closeness of the isoseismals, which is indicative of a rapid decline in 

 intensity from the epicentre outwards. 



Fig. 2. 



-Map of the Derby earthquake of May 3rd, 1903. 



p.*-- 



' I Alfre°tLn 



Derby 



Scale of 3Iiles 

 -J 4 6 8 



Kature of the Shock. 



In most places, the shock is described as a sudden shiver or short 

 tremor, its average duration being about 3^ seconds. Of the 36 

 observers who refer to the nature of the shock, 29 distinctly state 

 that it consisted of only one part, and the remainder do not enter 

 into details. The shock was, therefore, not a twin, but due to a 

 disturbance within a single continuous focus. 



