﻿Vol. 6 1." 



TWIIS-EARTHQUAKES. 



25 



the originating fault ; and, in the neighbourhood of the epicentre, 

 the distances between successive isoseismal lines are greater on the 

 side towards which the fault hades than on the other side. In fig. 1 

 (below) the isoseismal lines corresponding to two foci are represented 

 by dotted curves, and the impulses are supposed to differ in intensity, 

 so that while, for the western focus, three isoseismal lines (of 



Fig. 1. — Eccentricity of isoseismals in twin-earthquakes. 



intensities 5, 4, and 3) can be drawn, for the eastern focus there are 

 only two isoseismal lines (of intensities 4 and 3). The resultant 

 isoseismal lines would be drawn in the form represented by the 

 continuous curves. Thus, when the two impulses differ in intensity, 

 as in the Leicester earthquake of 1893, the Hereford earthquake of 

 1896, the Carlisle earthquake of 1901, or the Derby earthquake of 

 1904, the most marked characteristic of the resultant isoseismal 

 lines is the excentricity of the inner curve with respect to the 

 others. 



