A requirement currently exists in both mineral exploration and environmenta
l or engineering geophysics for a technique to model the magnetic fields ca
used by bodies with large to extreme susceptibilities in which both induced
and remanent magnetizations are significant. It is well known that modelli
ng such magnetic fields is not amenable to any known approximation. It is a
significantly difficult task that requires the solution of a magnetostatic
boundary value problem. Analytical solutions to the problem are extremely
useful for providing insight but generally of limited application in practi
cal interpretation due to the geometrical complexity of real situations. Av
ailable numerical solutions include both volume and surface integral equati
on formulations. However neither of these are particularly efficient for th
e purpose. An alternative surface integral equation formulation is presente
d here which represents the required magnetic field in terms of a double la
yer over the surface of the body. The technique accommodates both remanent
and induced magnetization and is generally applicable to any 3D body in a m
agnetic environment for which the Green's function is available. The presen
t technique has significant advantages over other integral equation solutio
ns in the geophysical literature. It is particularly economic in terms of t
he density of the surface discretization and consequently the computational
effort. Moreover, it is extremely robust. It is found to yield accurate so
lutions for the type of thin bodies that cause numerical instability with o
ther surface integral equation approaches. (C) 1999 Elsevier Science B.V. A
ll rights reserved.