Changes

==Interpreting fault throw==

==Interpreting fault throw==

There is a fairly reliable way to determine the direction of throw of certain basement faults from magnetic maps. Faults that vertically offset basement or other magnetic sources generally show abrupt amplitude changes of magnetic anomalies, both the highs and lows. In the figure below, a series of four northeast-trending magnetic anomalies on the west (two highs, two lows) abruptly loses amplitude along a northwest-trending line (A–A′) that crosscuts them. The high and low magnetic trends can be identified easily on both sides of this obvious down-to-the-east fault. The four anomalies disappear altogether along another northwest-trending line farther east (B–B′). This may be a strike-slip fault, which is not common in this area, or another down-to-the-east fault that has down-dropped the four anomalies beneath the level of detection—the preferred interpretation.

 

 

There is a fairly reliable way to determine the direction of throw of certain basement faults from magnetic maps. Faults that vertically offset basement or other magnetic sources generally show abrupt amplitude changes of magnetic anomalies, both the highs and lows. In [[:file:using-magnetics-in-petroleum-exploration_fig14-9.png|Figure 1]], a series of four northeast-trending magnetic anomalies on the west (two highs, two lows) abruptly loses amplitude along a northwest-trending line (A–A′) that crosscuts them. The high and low magnetic trends can be identified easily on both sides of this obvious down-to-the-east fault. The four anomalies disappear altogether along another northwest-trending line farther east (B–B′). This may be a strike-slip fault, which is not common in this area, or another down-to-the-east fault that has down-dropped the four anomalies beneath the level of detection—the preferred interpretation.

==Interpreting shear zones==

==Interpreting shear zones==