Estimating depth and model type using the continuous wavelet transform of magnetic data

Abstract

The continuous wavelet transform has been proposed recently for the interpretation of potential field anomalies. Using Poisson wavelets, which are equivalent to an upward continuation of the analytic signal, this technique allows one to estimate the depth of burial of homogeneous field sources and to determine the nature of the source in the form of a structural index. Moreau et al. (1999) accomplish this by successively testing the least‐squares misfit on a log–log plot of the wavelet transform amplitude versus the sum of the depth and the dilation (upward continuation height). We extend this methodology by analyzing the ratio of the Poisson wavelet coefficients of the first and second orders. For simple pole sources, this ratio at one dilation is enough to estimate the depth and index uniquely; but for extended sources of finite size, we must analyze the variation of the estimates with dilations. The technique gives good results on synthetic and field examples.

Multi-deconvolution analysis of potential field data

“…However, good agreement was observed between the TG anomaly calculated from the observed data and TG anomaly calculated from the estimated parameters. Vallee et al (2004) showed that a theoretical data from a dike source located at a depth of 143 m match the observed magnetic anomaly. Thus, it seems that the errors in the derived depths are likely to be due to small deviations of the source from an assumed idealized geometry and possibly also due to noise.…”

“…with several authors (Salem and Smith, 2005;Vallee et al, 2004) who estimated a structural index of thin dike (≈ 1) on the same anomaly.…”

Global nonlinear optimization for the interpretation of source parameters from total gradient of gravity and magnetic anomalies caused by thin dyke

“…Figure 14 depicts the fitting between the measured amplitude of 2-D analytical signal and model amplitude. A borehole taken at that location intersects the bedrock at 41 m (Vallee et al 2004). …”

Improved Local Wavenumber Methods in the Interpretation of Potential Field Data

“…In the case of airborne surveys the technique will be unable to give reliable solutions for dykes separated by less than four times the flight height if the dykes outcrops. Figure 5a shows an aeromagnetic flight line over a dike in the Matheson area of northern Ontario, Canada (ONTARIO GEOLOGICAL SURVEY, 2000;VALLÉE et al 2004). We digitized the profile from , and the sampling interval is 12 m. The magnetic sensor was located in a bird about 70 m above the ground.…”