178 



REID ET AL. REPORT OX NOMENCLATURE OF FAULTS 



Figure 



reverse Fault due to an oolique 

 Slip. 



determined by the displacement of the stratum, has caused an extension 

 at right angles to the fault strik ». It is evident that if the hanging wall 

 had moved, as in figure 8, with the stratum dipping as there represented, 



we should have had a normal 

 fault and a contraction at right 

 angles to the fault strike. The 

 relations of the two parts of 

 the disrupted stratum in fig- 

 ure 7 are exactly the same as 

 if we had had a simple reverse 

 dip-slip fault, and in figure 8 

 as if we had had a simple nor- 

 mal dip-slip fault ; and if there 

 were no disrupted dikes or 

 other means of determining 

 the amount of the strike-slip, the movements described could not be dis- 

 tinguished from simple dip-slip faults. It very frequently happens that 

 nothing more than the apparent displacement of the strata can be deter- 

 mined, and we recommend that the terms "normal" and "reverse" faults 

 as defined be used purely for 

 purposes of description and not 

 for the purpose of indicating 

 extension or contraction, tension 

 or compression, vertical or hori- 

 zontal forces. John A. Eeid has 

 suggested that the terms "appar- 

 ently normal" or "apparently 

 reverse" fault be used until it 

 has been definitely made out 

 whether the hanging wall has 

 experienced a relative movement figure 

 up or down the fault dip, and 

 then to use the terms "normal" or "reverse." The objection to this is 

 that it breaks with former usage and introduces confusion, for the dis- 

 tinction would certainly not always be made. 



normal Fault due to an oolique 

 Slip. 



SPECIAL CLASSES OF FAULTS 



There are two kinds of faults which have played such important roles 

 in altering the structure of some regions that they have received special 

 names. 





