PARALLEL DISPLACEMENTS 



181 



other in the other part. We can, of course, determine the perpendicular 

 distance between them by revolving the fault-plane about its trace until 

 it becomes horizontal; the original of a point, /, of the line ef, whose* 

 depth is fg (found by laying off the dip-angle S' at h', where the perpen- 

 dicular from / to the fault trace falls) will be brought to g" , where 

 h' g" = ¥ g; and the line ef will be brought to eg". The perpendicular, 

 e' n, dropped from e' to eg" , will give the amount of the displacement at 



FlGUItE 



Determination of the Shift, Case I 



right angles to the original of edj on revolving the fault-plane back to its 

 proper position, n will come to p, and e' p will be the horizontal projec- 

 tion of this displacement. 



Given, in addition, the trace and dip of a disrupted dike. If we are 

 fortunate enough to find a dike which has been cut by the fault-plane, 

 and whose traces are represented by T" and t", we can determine the 

 whole shift; if will be the projection of the line of intersection of the 

 undisturbed dike with the fault-plane, and f, its intersection with the 



