Edge detection and gravity sources depth estimation of southwestern Sirt Basin Libya, from gravity anomaly data

Abstract

Understanding the subsurface geologic structure of a region often require indirect geophysical approaches; this study delineates the edges and estimates the depths of gravity source bodies to achieve this for the study area. The gravity data was provided by the Libyan Petroleum Institute. Low-pass filters were used to separate the residual and regional components of gravity dataset, while the horizontal gradient magnitude (HGM), tilt derivative ratio (TDR), and the analytic signal ration(AS) methods were applied to delineate and estimate the depth of gravity source bodies. The study area is located in the Southwestern part of Sirt Basin, Libya. Spectral (matched filtering) analysis of the Bouguer gravity anomaly reveals to equivalent layers with some additional noise, corresponding to shallow and deep density contrasts with mean depths of 2.5km and 8.5km respectively.by applying the horizontal gradient magnitude and tilt derivative methods to the Bouguer anomaly map, distinct geologic trend faults were identified along the NE-SE, N-S, and NW-SE directions, with the NW-SE trend corresponding to the Gattar Ridge structure. Additionally, analytic signal depth estimates (0.4-5km; mean 2.7km) closely match the matched filter depth of 2.5km, reinforcing the result. The combined appraisal of source edge locations and gravity source depth estimates offers useful information on underlying basement configuration, which is highly essential for exploration targets that are mostly obscured.