CDI Versus inversão: aplicação a dados reais

Abstract

The aim of this paper is to carry out a comparison between two types of 2D electromagnetic modeled sections normally used on AEM data quantitative interpretation especially on those obtained from ATDEM measurements (ATDEM). One is obtained from fast modeling of the secondary magnetic flux decay and is the most common quantitative interpretation tool. The other is of more restrict usage and use 1D inversion techniques. In the first case, the technique transforms the ATDEM responses on a conductivity depth image (CDI) and a glimpse of the subsurface conductivity distribution can be obtained with a fast processing approach. In the second case, the use of a 1D inversion, based on the NLSTCI computational algorithm (short for nonlinear least-squares inversion of transient soundings for a central induction loop) allows to get a similar result but now relying on a wave equation development. It is a mathematically and computationally complex, and more time consuming technique. The two approaches were applied to airborne GEOTEMTM system real data, collected on a survey at San Pedro Valley (Southeast Arizona) in 1997.The available data from this region were made available by the USGS and were used in this quantitative analysis. As such, 2D sections were obtained, and from these, maps were generated. The results from 2D sections - conductivity spatial distribution obtained from CDIs and 1D inversions - were volumetrically interpolated (voxels) allowing a 3D representation of the conductivity spatial distribution for the surveyed area.