Chap. 8] 



MAGNETIC METHOD 



397 



AH = 2kZo log, 





(8-61c) 



AZ = 2*cZo(^3 -{- <P\ — <Pi — ip2) . 



The same rules in respect to maxima, minima, and zero points apply as 

 for the infinite dike. However, since the lower end becomes effective, 

 positive curvature values appear on the sides, and the maximum in vertical 

 intensity is flanked by two minima. 



For a horizontal slab, the horizontal transverse magnetization is generally 

 not negligible, and the anomalies 



J 



AH = 2k Ho sin a{ipA — fz -\- <pi — <pi) + Zo log. 



TiTz. 



AZ 



= 2/c Ho sin a 



> (8-61d) 



lOge — Zo(<Pi — (fS -{- <P2 — (fl) 



nn 



The horizontal intensity has a maximum over the southern and a minimum 

 over the northern edge. The maximum in vertical intensity occurs over 

 the middle of the slab and is flanked by two minima in the north and 

 south. 1 



The complete magnetic anomalies of a slope are 



AH = 2k sin i 



< Ho sin a sin t(<^2 



(fi) — cos i logj 



+ Zo sin i lo 



ge - + COS i{ip2 — ipi) 

 ^1 



AZ = 2k sin i 



K Ho sin a I 



) (8-61e) 



r2 



sin i loge — + cos {{(p^ — <pi) 



Zq 1 sin i(ip2 — (fi) — cos i loge — 

 L n 



])■) 



The transverse horizontal magnetization may be neglected when the strike 

 is nearly meridional and in high magnetic latitudes. The horizontal in- 

 tensity rises gradually to a maximum near the upper edge of the slope 

 and drops rapidly past it if the slope is upward in the x direction, as shown 

 in Fig. 8-52. If the slope is downward in the same direction, the hori- 

 zontal intensity shows a minimum of the same general character. The 

 vertical intensity rises from a minimum on the south side of the slope 

 through zero to a maximum over the upper edge. Downslope in the 

 X direction the vertical intensity passes from a maximum through zero 

 to a minimum. For very gentle slopes the gradient of gravity and, hence, 

 the horizontal intensity is very nearly constant, particularly, for meridional 

 strike or high latitude. 



