170 BEFD ET AL. REPOET OX NOMENCLATURE OF FAULTS 



fault to the strike of the strata that special subclasses are generally 

 recognized. 



A strike fault is one whose strike is parallel to the strike of the strata. 



A led ding fault is a special form of strike fault whose surface is paral- 

 lel with the bedding of the stratified rocks. 



A dip fault is one whose strike is approximately at right angles to the 

 strike of the strata. 



An oblique fault is one whose strike is oblique to the strike of the 

 strata. 



These terms are, of course, not directly applicable in regions of un- 

 stratified rocks; but they might be used in such regions with respect to 

 the strike of a system of parallel dikes if this were distinctly stated in the 

 description of the faults. 



Similarly with regard to the general structure of the region : 



A longitudinal fault is one whose strike is parallel with the general 

 structure. 



A transverse fault is one whose strike is transverse to the general struc- 

 ture. 11 



SLIP 



The word "slip" indicates the displacement as measured on the fault 

 surface; the qualifying words refer to the strike and dip of the fault. 



The slip, or net slip, is the distance, measured on the fault surface, 

 between two formerly adjacent points situated, respectively, on opposite 

 walls of the fault. It would be represented by a straight line in the fault 

 surface connecting these two points after the displacement : ah in figures 

 2 and 3. 12 



The strike-slip is the component of the slip parallel with the fault 

 strike, or the projection of the net slip on a horizontal line in the fault 

 surface : ac in figures 2 and 3. 13 



The dip-slip is the component of the slip parallel with the fault dip, or 

 the projection of the slip on a line in the fault surface perpendicular to 

 the fault strike: be in figures 2 and 3. 14 The strike-slip and dip-slip are 

 rectangular components of the net slip. 



The trace-slip is the component of the slip parallel with the trace of a 

 bed, vein, or other surface on the fault plane. 



The perpendicular slip is the component of the slip at right angles to 

 the trace of a bed, vein, or other surface on the fault plane. It equals 



11 See the word "flaw" further on. 



12 Spurr and Tolman call this the "total displacement." 



13 Tolman calls this the "horizontal displacement." 

 u Tolman calls it the "normal displacement." 



