Computation of geophysical magnetic data for a buried 3-D hexahedral prism using the Gauss-Legendre quadrature method

摘要

A new method is presented for the 3-D forward modelling of the magnetic effects (induced magnetization) of a hexahedral (trilinear) prism using the Gauss-Legendre quadrature method. The 3-D forward modelling provides an improved application to geological problems. The magnetic effect has been evaluated via the summation of the effects of the point dipole that fills the volume. The 3-D volume is divided into smaller prisms using an appropriate number of nodes. The algorithm is tested on two synthetic examples, and the results are compared against calculated data from a common program developed at the University of British Columbia-Geophysical Inversion Facility, with both tests showing positive results. The results of testing the algorithm against two synthetic slab models are also given. Finally, the program is applied to a field data set from Aynak-Logar Valley region in Afghanistan. Using this program, complex 3-D model bodies may be constructed from hexahedral prisms to facilitate the calculation of their magnetic anomalies and magnetic susceptibility. Interpretation of the results shows that 3-D constructed models are successful in recovering the shape and location of the true model.