STKUGTURAL RESULTS OF FAULTING. 



173 



If S is a minus angle (the case sliown in the figure) the curve will be 

 horizontal when 



— sin <5 ^r y/ln 10 sin /6^, 



or when 



y- 



— sin (5 

 InlOsinyff' 



but if S is a positive angle (falling in the same quadrant with /?) the curve 

 will have no horizontal tangent. 



Fault involving double curvature. — As lias already bceu poiuted out, since gravity 

 is likely to be an insignificant force compared with other forces acting on 

 the sheets of a faulted country, it is a matter of indifference whether we 

 regard the actual motion of the foot wall as upward or that of the hanging 

 wall as downward. If, therefore, contrary to the assumption thus far made, 

 the foot wall instead of the hanging wall were divided into sheets, and if the 

 latter were to sink relatively to the former, we should get a I'eversed loga- 

 rithmii- curve asymptotic to the original surface of the foot wall; and other 

 things remaining equal, its equation would be 



i/=:A{\ — nf) + X tan S. 

 If the rock on both sides of the fissure is the same, or possesse.s the 



-Double fault cur 



same phy.sical properties, and is divided into plates of the same thickness, 

 the energy brought to bear at the fissure will be distributed in Itoth direc- 



