Gravity and magnetic data are cost-effective methods to derive basement depth estimates and basin interface

We use a combination of approaches processing magnetic and gravity data that enables interpretations that provide an overview of the depth and structure of deeply buried basement. Aeromagnetic data offers a view of regional basement structures and reveals deformation at the junction between cover to basement.

The main structures related to magnetic basement depth determine the structural character and post-processing allows the extraction of magnetic sources close to the cover/basement interface.

Independent basement depth estimates – using our in-house developed software

Eslan Labs fuses the available data sets using the most up to date stable multi-scale horizontal and vertical derivative algorithms.

Our experts use an integrated approach involving a combination of the tilt-depth and spectral inversion methods to determine the basement depth and enhanced derivatives and Euler deconvolution to characterize structure.

Applying multiple methods to the same anomaly greatly improves the reliability of basement depth results. Fusing gravity and magnetic data builds an overview of the deep basins.

No single basement depth estimate method is best overall

At present there is no standard in selecting a reliable basement depth solution. Each basement depth estimation method has advantages, but all rely on the analysis of the anomalous gravity or magnetic field to determine basement depth and location of sources. They tend to identify the upper edges/corners of magnetized geologic structures since they use higher-order derivatives of the magnetic field, so enhancing the shallower anomalies.

In order to produce an accurate basement depth solution, Eslan Labs uses a range of complementary methods including spectral, analytic signal, tilt derivative, and extended Euler convolution, together with experience and geologic and geophysical knowledge but universally, determining basement depth requires stable derivatives.

Euler methods commonly produce a confusingly large number of solutions and so we developed methods of focussing these solutions by statistically identifying significant source solutions, and discarding noise.

This means that estimates of basement depth on basin flanks are well-resolved but the deepest parts of basins are often underestimated.

It is easy to calculate the derivatives used for qualitative interpretation such as the lineament analysis, but it is difficult to calculate derivatives required by quantitative analyses such as basement depth interpretation.

All our methods avoid both user bias, unstable generation of vertical derivatives using the FFT-tools, and the problematic moving window algorithm underpinning many commonly used methods that causes scattering of solutions from interference,

We use a rigorous approach to fuse the range of resulting basement depth solutions, so the solutions are more reliable than single solution depth estimates related to individual anomalies compared to clustered solutions.

Structure inferred from a fusion of gravity and magnetic to basement depth estimates provides insight into the evolution of basin compartmentalization, salt kinesis, and localization of reservoir-bearing structures in areas where the inherited basement architecture has affected basin evolution and development.

Hydrocarbon migration within a basin is often controlled by structures in the cover located over basement faults


Basement depth estimates compare with wells and seismic interpretation and illustrate the utility of the method at varying scales to estimate and map the depth to basement and structure, especially where data are scarce.

Spectral Inversion

The use of spectral methods for the inversion of magnetic and gravity data to determine depth to basement has been known for decades (Odegard and Berg,1965 and Bhattacharyya and Leu,1975).

Gravity and magnetic fields are linear systems, and this can be applied to inverting for the basement depth containing a mixture of shapes.

Mapping the basement depth means calculating the average radial log power spectra over a window of a magnetic or gravity field, the negative of the slope of which spectra is twice the depth to the center of mass of the bodies.

Our automated technique steps the spectral window over the grid only at the location of anomaly peaks, thus ensuring clear basement depth estimates.

Data points are edited to ensure that the basement depth estimates are in agreement with well TD’s, seismic interpretations, and geological data. We also use this technique to determine Moho depth, crustal basement thickness, continental lithosphere thinning and ocean-continent transition location.

Tilt Depth

The tilt-depth method of determining the variation in basement depth of magnetic source bodies provides a fast initial mapping of a sedimentary basin in terms of fault structure, dip direction of faults and basement depth.

The tilt-depth method can display high accuracy in ambient magnetic fields such as determining basement depth in basins that are not complex, but we find that this method is not of universal applicability.

Since the amplitude of the tilt derivative does not contain information on the strength of the geomagnetic field nor magnetization of the causative body, the susceptibility contrast across faults is derived from the derivative of the analytic signal that provides an effective means of defining the basement depth.

We prefer the tilt-depth method of determining basement depth to the Euler methods because it produces single solutions compared to Euler’s poorly constrained clusters of multiple solutions.

Euler Deconvolution

Current Euler methods of automating depth to source from potential field data are capable of providing solutions to basement depth and structural indices.but exhibit significant weakness because it generates massive numbers of spurious solutions, requiring statistical clustering to select the most realistic.

We have adapted an approach to Euler deconvolution suitable for accurate basement depth studies that uses the application of an n-order vertical derivative of the field, which suppresses the background field, reduces regional trends and mitigates problems of interference between anomalies, simultaneously solving the position of sources and structural index in the depth to basement problem.

We have adapted this Euler method to generate solutions of basement depth only at anomaly peaks, free from clusters of weak and misleading solutions.


At Eslan Labs we apply a combination of automated interpretation procedures, based on multiscale analysis and three-dimensional visualisation methods, to extract geometry from potential field data sets.

Gravity and magnetic data  constrain geometries with depth and edge location, typically with a variable degree of automated input. We use techniques designed to extract  the main features in a potential field. By using multiscale wavelet theory, these features have a rigorous relationship to contacts between zones of different density or magnetic susceptibility, and can be employed in an inversion strategy.

Multi-scale edge mapping is a process of mapping edges in potential field data at a variety of spatial scales, the shape of which are a function of the 3D location of contacts between bodies of contrasting density and/or magnetic susceptibility. Such surfaces provide a powerful tool for insight into the geometries of geological structures at exploration depth.

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