Faults are disruptions of the rock which commonly act as seals for hydrocarbon traps and sites of mineralization. Fault motion may involve earthquakes, wherefore the assessment of the displacement across faults may be of economic importance. This tectonic setting of faults is discussed in the first paragraph. The fault surface can move in different ways. The actual movement of the fault is the basis for the classification of faults. The difference between the major classifications fault slip an fault separation is explained in the second section. The effect of different faultings on the map patterns follows, and map symbols to facilitate the reading of geological maps are explained. Finally, the map analysis of faulte strata in areas of rugged topography is outlined in the sixth section.