Integrated gravity-based structural characterization of the Sana’a Basin, Yemen using WGM2012 data, spectral analysis, and GM-SYS modeling

The Sana’a Basin is one of the most important intramontane basins in Yemen, hosting significant groundwater resources and a complex geological succession influenced by regional tectonic processes associated with the Afar Triple Junction, Red Sea rifting, and Gulf of Aden opening. Despite extensive geological and hydrogeological investigations, uncertainties remain regarding the deep structural framework, basin geometry, and tectonic controls governing its evolution. This study investigates the subsurface architecture of the Sana’a Basin through the integration of satellite-derived gravity data, geological information, borehole records, spectral analysis, and gravity-constrained forward modeling. Gravity data extracted from the World Gravity Model 2012 (WGM2012) were processed using Oasis Montaj v8.3 through terrain correction, Complete Bouguer anomaly calculation, frequency-domain filtering, and regional–residual anomaly separation using a first-order Butterworth filter with a cutoff wavelength of 20 km. Structural lineaments were subsequently extracted using the Centre for Exploration Targeting (CET) Grid Analysis tools. Radially Averaged Power Spectrum Analysis identified two principal source populations at average depths of approximately 2.8 km and 4.25 km. The shallower depth is interpreted as reflecting major density contrasts within the volcanic-sedimentary succession, whereas the deeper component represents a major basement-controlled structural level governing the long-wavelength gravity field and basin architecture. These interpretations were independently evaluated using lithostratigraphic information from deep exploratory wells (DS-1 and DS-2) and fence-diagram correlations constructed from twenty-three boreholes distributed across the basin. To further constrain subsurface geometry, 2D gravity forward models were developed along NW–SE and NE–SW profiles using the GM-SYS module. The resulting models achieved satisfactory agreement between observed and calculated gravity responses, with RMS misfits of 0.934 and 3.2 respectively. The interpreted structure reveals a fault-controlled basin architecture characterized by normal faulting, basement segmentation, asymmetric graben-like geometries, and significant spatial variations in volcano-sedimentary thickness. The Integrated interpretation indicates that the Sana’a Basin evolved under prolonged extensional tectonics associated with regional rifting processes. Structural trends are dominated by NW–SE-oriented fault systems accompanied by subordinate NE–SW and NNW–SSE trends, reflecting multiple tectonic deformation phases. The strong agreement among gravity anomalies, spectral depth estimates, borehole information, fence-diagram correlations, and GM-SYS models demonstrates the reliability of the adopted methodology and provides a robust geophysical framework for future geological, hydrogeological, and three-dimensional subsurface investigations within the basin.