Source ambiguity from an estimation of the scaling exponent of potential field power spectra

An analysis of the field scaling power spectrum yields useful information a bout the source distribution, but it is uncertain whether deterministic, ra ndom, fractal or mixed approaches have to be used for the interpretation. T o this end, the scaling properties of potential field spectra are analysed for a number of different source models of geological interest. Besides the models of Naidu (purely random sources) and Spector and Grant (gross block statistical ensembles) we consider other types of density and magnetizatio n distributions with spectral exponents in the fractal range, such as a sin gle homogeneous body with a random white source distribution. Spectral slop es in the fractal range are obtained. We also study the effects of important natural sources, such as salt domes and sedimentary basins, representing them with simple Gaussians or combinat ions of Gaussian signals. The same spectral slopes as for gravity signals g enerated by 3-D fractal source distributions are found for them. Hence the power law decay of the field is not a characteristic only of fractal source models. If a 3-D fractal source distribution is assumed a priori, a way of verifyin g the goodness of the model is to examine the whitened field at source leve l. The probability that the whitened field derives from a random white popu lation is estimated for synthetic and real anomalies by applying the usual statistical tests.