The calculated anomaly has two components, one vertical and one horizontal. Note that this anomaly is the measured magnetic field after the total magnetic field, at the time of formation of the lithosphere, has been removed. These components are given, respectively, by the following equations

(1) |

(2) |

where

(3) |

(4) |

and additionally

Here the is the magnetization vector where its horizontal and vertical components are, respectively,

The magnetic anomalies that are measured arise due to magnetization of the oceanic floor and this magnetization is by induction, that is where k is the magnetic susceptibility and is the total magnetic field. Here I is the inclination of the total magnetic field, D is the declination and B is the strike of spreading direction clockwise from north.

The total anomaly vector is a projection of its horizontal and vertical components along the direction of

(5) |

Magellan's algorithm is based on these equations and assumes that the total field is either in the direction of Earth's current magnetic field or in the reverse direction. For instance if we are calculating the contribution from a block that is reversly magnetized then we multiply with a minus sign which results in a negative contribution from that block.

Ásdís Benediktsdóttir 2009-02-21