﻿DK. CHARLES DAVISON ON THE 



[Feb. 1905, 



duration of the sound was greater than, equal to, or less than, that 

 of the shock : — 





Beginning. 



End. 



Relative 

 Duration. 



P 



70 



57 



50 

 62 



c 



23 



39 



25 

 31 



/ 



7 

 4 



25 



8 



P 



10 



7 







8 



c 



51 

 71 



56 



61 



/ 



39 

 21 



44 



32 



9 



73 



51 



29 



58 



e 



27 

 46 



43 



38 



I 

 



29 

 4 





Between isoseismals 5 and 4. . . 



Between isoseismal 4 and 1 

 boundary of sound-area . J 



Whole sound-area 





IV. Origin of the Earthquakes. 



Taking first the earthquake of 1893, we obtain from the seismic 

 evidence the following elements of the originating fault in the 

 neighbourhood of the north-western focus : — (1) the mean direction 

 of the fault is from W. 30° N". to E. 30° S. ; (2) the hade is to the 

 north-east ; and (3) the fault-line passes a short distance to the 

 south-west of the centre of the isoseismal 5, or about 1 or 2 miles 

 to the south-west of Woodhouse Eaves. For the south-eastern focus, 

 the elements are less clearly defined : — (1) the mean direction of 

 the fault lies between that given above and north-west to south- 

 east; (2) the hade is to the south-west; and (3) the fault-line 

 passes a short distance to the north-east of the centre of the 

 isoseismal 4 corresponding to the south-eastern focus, or not far 

 from Tugbj. These two sets of conditions are consistent with the 

 existence of a single fault, in which the direction of hade changes 

 in a district about midway between Markfield and Tugby. 



It may be remarked that this change of hade furnishes an ex- 

 planation of the divergence of the axes of the resultant isoseismal 

 lines of PL I. For, at the north-western focus, the isoseismal 4 

 diverges farther to the north-east than in the opposite direction ; 

 while, at the south-eastern focus, it diverges farther to the south-west 

 than to the north-east. Thus, the axis of the resultant isoseismal 7 

 should be tilted more towards the north-west ; and the same should 

 hold true of the resultant isoseismal 3. 



Again, for -the principal earthquake of 1904, the elements of the 

 earthquake-fault are: — (1) the mean direction of the fault is from 

 W. 42° N. to E. 42° S. ; (2) the hade is to the south-west; and 

 (3) the fault-line passes a short distance to the north-east of the 

 centre of the isoseismal 5, and therefore not far from Tugby. It 

 is thus probable that the earthquakes of 1893 and 190 4 

 originated in one and the same fault. 



