Structural mapping using ground magnetic data and enhanced derivative techniques in the Assam-Arakan Basin, northeastern India

Abstract

The study area lies in the structurally complex and tectonically active northeastern margin of India, near the Himalayan foothills and within the Belt of Schuppen of the Upper Assam foreland shelf. Accurate mapping of subsurface structures is critical for hydrocarbon exploration in this region, where conventional seismic methods are challenged by rugged topography and poor signal penetration-particularly in shallow zones dominated by boulder-sandstone formations. To address these limitations, ground magnetic data are less influenced by surface conditions and can provide valuable insights into lateral lithological variations, structural discontinuities, and the geometry of magnetic source bodies. Ground magnetic data were analysed using a suite of enhanced derivative techniques aimed at delineating both shallow and deep-seated structural features. Methods such as Total Horizontal Derivative (THDR), Analytical Signal (AS), Tilt Derivative (TDR), Horizontal Derivative of Tilt Derivative (HDTDR), and Theta Map Analysis (TMA), were applied to processed magnetic anomalies to highlight fault trends, lithological contacts, and magnetic source boundaries. THDR emphasized sharp lateral contrasts, while the TDR and HDTDR enhanced edge detection and improved delineation of structural boundaries. The AS further contributed by producing amplitude maxima directly above causative bodies, reducing ambiguity linked to magnetization direction and thereby supporting depth estimation. These results facilitated improved structural clarity in the areas where seismic imaging remains inconclusive and provided with a valuable framework for guiding further exploration in the Assam–Arakan Basin. The integrated application of these methods reveals a structurally complex framework, marked by multiple fault systems, basement highs, and possible intrusive bodies, many of which correlate with known geological trends. These findings not only refine the understanding of the subsurface architecture but also identify geologically significant targets that warrant further investigation. The study demonstrates the value of combining reduced to pole (RTP), derivative filters, and cos (θ) analysis to strengthen magnetic interpretation in structurally complex regions for lineament analysis. The insights gained not only enhance the understanding of the subsurface framework in the Assam–Arakan Basin but also support the identification of new exploration targets for hydrocarbons and other resources.