Rapid joint imaging of multiple electromagnetic data sets

Abstract

Summary An algorithm is presented which allows electromagnetic data acquired from multiple surveys to be imaged jointly. By jointly imaging data sets, it is possible to create an image that is more representative of the ground than could be obtained from imag es created from each data set individually. The algorithm is based on an approximation to the integral equation method, and fast enough to be used for routine interpretation on standard personal computers. An example using simulated data illustrates the effectiveness of jointly imaging a helicopter electromagnetic data with ground based slingram measurements. Rather than solving a full regularized inverse problem, I present a rapid electromagnetic imaging algorithm that is based on an approximation to the integral equation forward modeling method. The algorithm is fast enough that it can be applied routinely t o interpret the large electromagnetic data sets typical of mining exploration, and can furthermore be used to jointly image multi ple data sets. Results of the algorithm are demonstrated on synthetically generated data, illustrating the case in which helicopte r electromagnetic (HEM) data are jointly imaged with slingram ground data. The example typifies many in mining exploration, and illustrates the how the algorithm is applicable to assisting interpretation in where both airborne and ground electromagnetic data are available,. Theory In the integral equation method, the embedded structure is repl aced by an equivalent volume of induced sources, where the induced sources S, are related to the total field F through some anomalous physical property contrast, p by F = p S (1) The measured electromagnetic response of the body (or data) D, at a measurement location rm is given by the integral over the volume of the anomalous volume containing induced sources, S, weighted by a Green function G