The AMS technique is based on the dependence of anisotropy of magnetic susceptibility on the alignment of the long- and short-dimensions of magnetic mineral grains within the sediment.

The magnetic susceptibility, K, of an individual mineral grain varies with direction as a result of the grain's shape and crystalline properties. This anisotropy of magnetic susceptibility (AMS) can be represented by a triaxial ellipsoid, the three principal axes of which correspond with the maximum, intermediate and minimum susceptibility values (Kmax, Kint, and Kmin) respectively.

The AMS of an assemblage of magnetic mineral grains within a sediment sample reflects the preferred alignment of that population of grains. In this case, Kmax defines the preferred orientation of grain long dimensions and Kmin that of the short dimensions.

The AMS method provides a precise specification of the 3-D alignment of the entire population of magnetic mineral grains within a sample, in a fraction of the time required for conventional petrofabric measurements.