Discussion on `Spectral analysis of aeromagnetic data for geothermal energy investigation of Ikogosi Warm Spring - Ekiti State, southwestern Nigeria’

Levi Ikechukwu Nwankwo

doi:10.1186/s40517-014-0011-3

Abstract

The recent paper by Abraham et al. (2014) `Spectral analysis of aeromagnetic data for geothermal energy investigation of Ikogosi Warm Spring - Ekiti State, southwestern Nigeria’ applied spectral analysis in the interpretation of aeromagnetic data for estimation of curie-point depths using a data window of 55 × 55 km; however, the employment of such small window may not be consistent with derived curie-point depth results. Here, I would like to clarify and point out the possible errors in the paper. It is suggested that the curie-point depth results be re-computed with appropriate window width. This would tremendously assist researchers in appropriate spectral calculation and curie-point depth investigations.

Highlights

The recent paper by Abraham et al (2014) ‘Spectral analysis of aeromagnetic data for geothermal energy investigation of Ikogosi Warm Spring - Ekiti State, southwestern Nigeria’ applied spectral analysis in the interpretation of aeromagnetic data for estimation of curie-point depths using a data window of 55 × 55 km; the employment of such small window may not be consistent with derived curie-point depth results
Window sizes are chosen to focus on different depths of investigation; small windows target shallow depths, as the shallow sources produce high-frequency anomalies, and larger windows target greater depths with deep-seated bodies (Archimedes Consulting 2013)
The purpose of this review is to clarify and point out the possible errors in the recent paper authored by Abraham et al (2014) regarding data window

Summary

Introduction

The recent paper by Abraham et al (2014) ‘Spectral analysis of aeromagnetic data for geothermal energy investigation of Ikogosi Warm Spring - Ekiti State, southwestern Nigeria’ applied spectral analysis in the interpretation of aeromagnetic data for estimation of curie-point depths using a data window of 55 × 55 km; the employment of such small window may not be consistent with derived curie-point depth results. Spectral analysis has been widely acknowledged as a robust method for automated depth estimations from magnetic anomaly data (Nabighian et al 2005). The approach considers the anomaly to be caused by an ensemble of magnetic sources in order to determine their average depth. Spector and Grant (1970) showed that logarithmic radial-power spectra of gridded magnetic data contain constant-slope segments that can be interpreted as arising from statistical ensembles of sources, or equivalent source layers, at different depths. The areal extent of the subset of data analyzed (the window) limits the maximum depth being investigated. Window sizes are chosen to focus on different depths of investigation; small windows target shallow depths, as the shallow sources produce high-frequency anomalies, and larger windows target greater depths with deep-seated bodies (Archimedes Consulting 2013)

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