Gridding gravity data using an equivalent layer

Gravity data are routinely gridded in preparation for contouring or imaging , or to enable processing by a fast Fourier transform method. Frequently us ed gridding techniques such as 1/r(N), minimum curvature, or kriging, inter polate data values with no regard to the nature of the data involved; they will produce the same interpolated values if either magnetic or gravity mea surements with the same numerical values are used. Equivalent layer griddin g however fits the known potential field data values using the geophysical response of a thin surface layer whose physical properties vary spatially. The response of the surface layer can then be calculated at any other point s for the purpose of interpolation. The interpolated data values will then depend on the nature of the data being used. A program to perform such grid ding (running under Windows'95 or '98) has been written and is available fr ee via ftp from ftp.cs.wits.ac.za in directory /pub/general/geophys. (C) 20 00 Elsevier Science Ltd. All rights reserved.