CONCERNING THE PROCESS OF THRUST FAULTING 435 



can be transmitted without rupture of the arches, and rupture 

 follows the forms outhned above (Fig. 6). In an analysis of the 

 conditions at the instant after rupture, let P be the total compres- 

 sive force, let G be the weight of the moving mass, let be the 

 angle of shearing at any one place, and let a represent the cross- 

 sectional area of the member. Then, as ChamberUn and Miller 

 show/ the intensity of thrust {pt) tangential to the shear plane is 



P sin 6 cos 9 

 Pt = 



a 



and the intensity of the normal stress (^„) is 



P sin^ e 



Pn = 



a 



Likewise, the force of gravity is resolved into tangential and nor- 

 mal components, the tangential opposing the tangential compo- 

 nent of the thrust, and the normal being added to the normal 

 component of the thrust. The tangential component of gravity is 



Gt = G X sin Q , 

 and the normal component is 



Gn=G X cos 9. 



The intensity of the tangential component of gravity is 



Gsin9 G . 



gi = 7-^ = — sm9tan9. 



a cot 9 a 



The intensity of the normal component of gravity is 



Gcos9 G . ^ 



Sn= -^ = -sm9. 



a cot 9 a 



Thus, after rupture the intensity of thrust becomes 



P sin 9 cos 9 G sin 9 tan 9 sin9 ,„ ^ ^ ^x 



= (Pcos9-Gtan9), 



a a a 



and the intensity of friction becomes 



/Psm'Q , G . ^\ sin9.„ . ^ , „. 



/x — sm9 =M (Psin9+G) , 



\ a a / a 



in which [x represents the coejficient of kinetic friction. 

 ' Jour. Geok, XXVI (1918), 15 ff. 



