
TY  - JOUR
A1  - S. Smith, Richard 
A1  - J. Lee, Terry 
T1  - The moments of a sphere in a uniform field, a versatile model
JF  - ASEG Extended Abstracts
JO  - ASEG Extended Abstracts
Y1  - 2001
VL  - 2001
IS  - 1
SP  - 1
EP  - 4
KW  - 
UR  - https://doi.org/10.1071/ASEG2001AB133 
N2  - The moments of a sphere in a uniform field can be used to approximately model the moments of a sphere in a dipolar field. The numerical computations are trivial and the approximation is especially good for higher-order moments. The greatest discrepancy is seen on the zeroth-order moment at large radii, however, the zeroth-order moment is not commonly used for interpreting airborne electromagnetic data. The sphere in a uniform field can also be used to approximate the response of a body that has its currents constrained to flow in a specific dip plane. This means that plate-like bodies or anisotropic spheres can also be modelled. The third-order moment of MEGATEMÔ data acquired over the Reid-Mahaffy test site shows an anomalous response than can be modelled by a sphere at 170 m depth with a conductivity of 15 S/m and a radius of 40 m. The currents flowing in the sphere are constrained to flow in a vertical plane. This model is consistent with the geology of the area and a hole drilled to test the anomalous zone. 
ER  -

