A graph method for interpretation of magnetic anomalies over 2D dikes and vertical faults

Abstract

Simple geometric assumptions for dikes and faults are often used for interpreting the parameters of these structures from magnetic anomalies. The magnetic anomaly of a 2D dike or a vertical fault consists of two components; one with even and the other with odd symmetries. The function resulting from the ratio of the even and odd components is independent from the amplitude coefficient. The abscissa of the half-maximum of the even component and the maximum of the odd component of a dike or a vertical fault is related to its depth and its half-width. Incorporating this relation into the corresponding equations for dikes and vertical faults, the half-width value can be eliminated from the equations. Thus, the resulting ratio can be used for determining the model parameters. Using the ratio of the even component to the odd component for given distances, curves can be obtained for different depth-index parameter pairs, and from the graph of these curves, parameters of 2D dikes and vertical faults can be determined. The validity of the method is tested using synthetic models for dike and vertical fault cases. The method is also implemented on two different field data, and the results obtained are compared to previous studies.

Keywords

• magnetic interpretation
• 2d dike
• vertical fault
• graph method.