Seismic aberrancy unraveling basement flexures: A study from northeast India

Abstract

The basement in the Upper Assam foreland basin, northeast India, is severely deformed and buckled. It is compartmentalized into several structural compartments. These compartments are breached with minute flexures (or fractures), which developed over the geologic period due to tectonic modifications by fault networks and overlying sediment loads. Flexure anomalies dominant within the basement interval are interpreted using high-quality 3D seismic data acquired from the basin. The data are spectral balanced and structurally conditioned to improve the visibility of suppressed and masked reflections. Attribute maps obtained by computing legacy seismic attributes like energy ratio-similarity and curvature are integrated to interpret flexure networks and associated deformed structures. An advanced seismic attribute called aberrancy is computed to complement the interpretations of the preceding legacy attributes. The aberrancy attribute prominently revealed the presence of flexure networks occurring within the basement interval in the study area. In addition, the geometric characteristics of flexure anomalies suggest that flexures are particularly intense in the northeastern (zone 1) and western (zone 2) parts of the basement. The intensity of the flexures within these zones varies between 0.3 and 0.6 m−1. Overall, the basement displays a low to moderate variation in the intensity of the flexures, with exceptions observed in the aforementioned zones. The method thus presented could be applied to similar tectonic settings to aid the interpretation of subtle deformed networks observed in seismic data.