PARALLEL DEVELOPMENTS 



185 



We have not fixed the fault-plane, but if the direction of the striae 

 have been determined it is probable that the strike and dip of the fault- 

 plane have been also. If they have, we can determine the projections of 

 the lines of intersection of the fault-plane and the stratum, as in case I 

 and figure 7; then draw a line parallel with the azimuth of the striae 

 connecting the two lines mentioned; the depths of the two ends of its 

 original can be found, and thus its dip and the total shift. 



If one side of the fault should be igneous and the other side stratified 

 rocks, we can in general infer which side has been relatively raised, and 



--'? 



Figure 10. — Determination of the Displacement of a Plane, Case V 



we may be able to estimate the vertical throw from the thickness of the 

 stratified rocks; but if the fault is diagonal with respect to the strata, a 

 further complication is introduced. By following along the fault we 

 may come to a place where the strata are horizontal; it is also possible 

 that traces of the stratified rock, which have not been entirely eroded off, 

 may be found on the igneous rocks, which would indicate the vertical 

 throw and the horizontal shift; but we could not, without finding the 

 hade of the fault, determine whether the fault were normal or reversed. 

 This, however, is rather a case of folded than of plane strata. 



