Utility of natural generalised inverse technique in the interpretation of dyke structures

Abstract

Forward and Inverse methods of magnetic interpretation have been used to estimate the parameters of dyke like intrusion over the eastern continental shelf of India. In the forward problem, the tentative parameters of the causative source are assumed and anomalies are calculated using the anomaly equation, while inverse problem refers to methods of tracing the boundaries or outlines of anomalous bodies using an iterative approach. While solving the inverse problem, data kernel has been generated through the model (i.e. partial derivatives of magnetic anomaly function with respect to model parameters at each station forming the kernel). In solving the coupled eigenvalue problem of covariance matrices of data kernel, Singular Value Decomposition (SVD) has been performed to build Generalised Inverse Operator (GIO). This GIO is operated on the observed anomaly (with reference to the calculated) to yield improved model parameters. Data and model resolution matrices are computed to check the correctness of the solution and further analysis. The marine magnetic total field anomaly of continental shelf of Visakhapatnam is interpreted using GI technique, which revealed the causative source of the anomaly as a dyke model at a depth of 120 m below seabed.