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Estimation of Horizontal Location and Depth of Gravity Anomalies using Normalized Full Gradient (NFG)

Document Type : Original Research Paper

Authors

1 Faculty of Mining Eng., Petroleum and Geophysics, Shahrood University of Technology, Shahrood, Iran

2 Schools of Geophysics and Information Technology, China University of Geosciences (Beijing), China

Abstract

Estimation of depth and horizontal location of anomalous bodies plays an important role for selecting exploration wells location. There are many methods for depth estimating, and most of them use high-pass filters. The Normalized Full Gradient (NFG) method is one of these methods that use Fourier series to remove deficiencies and eliminate the oscillations which appear on the downward continuation when passing through center of an anomalous body. In this paper, the main goals is calculation of NFG and present a new method for determining optimum number of Fourier terms and use them for synthetic and real two and three dimensional field data. The obtained results on synthetic data indicate that the estimated location and depth of the model is in 10 percent error with the real. The NFG method has also applied on two sets of real field gravity data to determine the location and estimate depth of Humble salt dome (USA) and massive sulfide mineralization of Mobrun (Canada). For the first field data set the NFG has provided a depth to the centre equal to 4.8 km and for the second case the depth to the top section of mineralized body has been estimated 17 meters and its continuation to a depth more than 70 meters has also been confirmed.  The obtained results of the NFG method on real field data in each case are in good agreement to those provided by other independent information arises from drilling and other geophysical methods. The above matter clearly illustrates that the NFG method is able enough to locate anomalous bodies and estimate their burial depth precisely.

Keywords

References
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Scientific Quarterly Journal of Geosciences
Volume 19, Issue 76
January 2010
Pages 169-176
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