176 REID ET AL. REPORT ON NOMENCLATURE OF FAULTS 



The throw is the vertical distance between corresponding lines in the 

 two fracture surfaces of a disrupted stratum, etcetera, measured in a 

 vertical plane at right angles to the fault strike. 



The heave is the horizontal distance between corresponding lines in 

 the two fracture surfaces of a disrupted stratum, etcetera, measured 

 at right angles to the fault strike. These distances must be measured 

 between corresponding lines — for instance, between the upper edges of 

 the two fracture surfaces of the stratum or between their lower edges — 

 but not between the upper edge of one fracture surface and the lower 

 edge of the other. 



In figure 2 the ends of the block are vertical sections at right angles to 

 the fault strike ; fk is the throw and ek the heave. In figure 3, eg is the 

 throw and og the heave, if the strikes of the fault and strata are parallel. 

 (See also figures 15, 16, 17.) The words "throw" and "heave" have been 

 used in various senses. A. G-eikie uses "throw" for the distance {ec, in 

 figure 9 ) , which we have called the vertical separation, and Spurr for the 

 separation along the dip of the fault plane. J. Geikie, Willis, Scott, and 

 Fairchild use "heave" practically as it is defined above. A. Geikie and 

 Spurr make it equivalent to the offset. Jukes-Brown apparently used it 

 for the strike-slip (de Margerie and Heim, page 72) ; so did Eansome, 

 and Scott also uses it in this sense when he refers to "heave-faults." The 

 throw has also been called the "vertical throw" and the heave the "hori- 

 zontal throw," but this usage is not recommended. 



APPARENT DISPLACEMENTS 



It is often desirable to refer to the apparent displacement in a par- 

 ticular vertical section. For this purpose it is convenient to use the ex- 

 pressions apparent slip, apparent throw, etcetera. The context should, of 

 course, show what vertical plane is under consideration. It is never 

 necessary to use the word "apparent" in connection with the separation, 

 as the separation can be measured in any given direction. 



FAULTS CLASSIFIED ACCORDING TO THE DIRECTION OF THE MOVEMENT 



Faults may be classified, according to the direction of the movement 

 on the fault plane, into 



Dip-slip faults, where the net slip is practically in the line of the fault 

 dip. 



Strike-slip faults, where the net slip is practically in the direction of 

 the fault strike. J. Geikie calls such faults "transcurrent faults," or 



