FAULT PROBLEMS IN FAULT PLANES
Fault problems are treated by sections in fault planes. Methods are given for deriving from strike and dip of fault and strike and dip of faulted planar elements, such as beds, veins, and dikes, the angles required for drawing in the fault plane. Methods are given for converting field observations on plunge and direction of plunge of linear elements on fault walls, such as grooves and striations, to pitch for drawing in the fault plane. The trigonmetric methods are reduced to substitutions in formulas. The methods using the meridional stereographic net or Postel net are rapid and give results within the limits of accuracy of most field observations. Trigonometric formulas and a net method for converting known thickness to apparent thickness on an inclined fault plane are given. Examples include translatory and rotatory faults affecting veins, ore shoots, and seams. Among the examples of transverse faults cutting folds is one having the features of some tear faults, in that fault movement was partly contemporaneous with folding of beds.