**4. Discussion and conclusions**

Gravity anomalies and depth estimation from airborne gravity data is presented. Spectral analysis approach can be used to design special filters for separation of complete Bouguer anomalies into the residual and regional components. The power spectrum from potential field data for depth interpretation using spectral analysis approach is always not straight due to randomly uncorrelated distributions of anomalous sources. The depth estimation technique using spectral analysis can be

*Gravity Anomaly and Basement Estimation Using Spectral Analysis DOI: http://dx.doi.org/10.5772/intechopen.99536*

### **Figure 8.**

*Residual component of the complete Bouguer gravity anomaly map. Estimated depths (D1 & D2) of each block (B01, B02, … , B17) of 55 km x 55 km with 50% overlap are shown for the sedimentary basement estimation. Gboko as well as the basement outcrops east of Ogoja are shown. Intrusions and locations of the anticline and syncline are superimposed.*

applied either in space or frequency domain. However, depth estimation of anomalous sources in frequency/wavenumber domain is simple and more reliable due to the fact that, in wavenumber domain, the convolution operator is conveniently transformed to multiplication notation using Fourier Transform. The estimation of depth from the approach is normally done from the slope of the logarithmic plot of the power spectrum against the wavenumber [12]. Geological and tectonic complexity of a region can be interpreted from the technique of spectral analysis. The drawback in using the approach of spectral analysis for depth interpretation, is that, the concept is based on an ensemble of prisms of frequency-independent randomly and uncorrelated distribution of anomalous sources equivalent to white noise distribution. That is to say, spectral analysis technique involves manually selecting a segment that correspond to certain wavenumber range from the power spectra to represents a detectable anomalous sources inside the earth.
