Estimation of the depth and boundary of gravity anomalies using improved Euler and phase congruency methods

In recent decades, the study and recognition of liniments has become an important matter in the field of geosciences. Liniments study is a routine practice for the interpretation of gravity data. It is important for a wide range of geological data. However, interpretation outcomes of gravity data are found to be highly variable among interpreters and lack consistency even within individual. Therefore, new methods have been presented to improve the reliability of structural interpretation, and these methods help interpreters to reach similar results from the same gravity data.

Potential field methods play a fundamental role in geophysical explorations. One of the main goals in the interpretation of potential field data is to determine the location and estimate the depth of magnetic and gravity anomalies. Quantitative interpretation methods of potential field data, such as standard Euler, have always been modified in order to increase the accuracy in determining the characteristics of subsurface sources, and generalizations have been made in order to improve the reliability of the results. Standard Euler is a method based on choosing the dimensions of the window and depending on the structural index. Therefore, defining a window with suitable dimensions and moving it within the data grid or profile and choosing the appropriate structural index can provide the results of this method with higher accuracy. Since the lack of accurate determination of the structural index can lead to wrong results in depth estimation, Euler's generalizations are presented to remove the structural index from the calculation process. Quality of the field data poses great influence on the Euler inversion solutions. If the data has low signal-to-noise ratio, the computational process will be masked. This issue makes it difficult to outline boundaries of the causative have sources.

In this research, in order to determine the location and estimate the depth of the gravity anomaly, another generalization of standard Euler using the singular value decomposition method and the ratio of the horizontal gradient to the analytical signal has been used. Also, the quantity of phase congruency was applied to the data in order to interpret the results more accurately. Compared to the standard Euler, the results of show more compliance with the anomaly boundary. Also, the depth estimation interval (bar graph) in the improved Euler is smaller than the standard Euler. For further investigation and order to increase the credibility of the interpretation, phase congruency has been applied to synthetic and real data in order to determine the location of the anomaly.