LOW-ANGLE FAULTING 30 
significance, it would suggest a strong tendency of layers near the 
surface to shear over less movable layers below. 
E. EFFECT OF WEIGHTING 
Although the piling up of faulted slices does not of itself cause the 
development of rotational strain, when the mass is subjected to 
horizontal compression, it may indirectly bring about that result 
by weakening the resistance of the upper portion owing to the 
Fic. 17.—Thrust fault in Chagrin shales. On Paine Creek, 6 miles east of Paines- 
ville, Ohio. Fault plane dips 15°S.W. Throw 1 ft.,; heave 2 ft. 11 in. Charles E. 
Decker. 
preliminary fracturing. If, in addition, the mass piled up is of 
sufficient magnitude, it may theoretically affect the result in 
another way owing to the fact that the additional weight of the 
piled-up mass adds a new force at right angles to the horizontal 
thrust. Figure 18 will illustrate the behavior of this force. In 
this diagram the horizontal thrust was taken to be three times the 
vertical force due to gravity. The resultant of these two forces 
will be inclined downward 18° 26’ from the horizontal. Frac- 
turing as the result of these two forces will be determined by the 
direction of this resultant of forces. As this is inclined 18° 26’ 
downward from the horizontal, faulting, even though it should take 
