Integration of Seismic Interpretation with Remote Sensing Techniques to Study the Neotectonics of the Fold-and-Thrust Belts of Northwestern Pakistan

The fold-and-thrust belts of Pakistan are actively deforming and consequently produced devastating earthquakes which destroyed many lives, infrastructures, and properties over the last century. This work focuses on three fold-and-thrust belts, located along the Main Frontal Thrust; from east to west, the Potwar Plateau, the Bannu Basin, and the Sulaiman Fold Belt. Coupled with these fold belts are curved structures referred to as re-entrants. The Sibi Re-entrant, located adjacent to the Sulaiman Fold Belt, has experienced many earthquakes in comparison to the Tank and Kalabagh Re-entrants. In order to understand the factors that control the formation of these re-entrants and fold belts, radar satellite image processing technique, InSAR (Interferometric Synthetic Aperture Radar), was utilized and integrated with other available data, such as seismic profiles, well logs, gravity, and multi-spectral satellite imagery mapping. The integration of InSAR using ten PALSAR images and seismic data shows that the Potwar Plateau is still tectonically active with areas uplifting up to 15 mm/yr. Based on seismic and well data, salt acts as the main detachment layer displaying thin-skinned deformation. In addition, salt tectonics is observed to be concentrated near the Main Frontal Thrust, where the overlying rocks are the weakest. The Tank and Kalabagh Re-entrants were interpreted as ‘basin-controlled’ curves with the presence and the extent of salt controlling the shape of re-entrants. Differential movement between areas containing salt and areas with no/lack of salt resulted in the formation of right-lateral strike slip faults (Pezu-Bhittani and Kalabagh faults) and in consequence their respective re-entrants.
In contrast, there is no clear indication of a major right-lateral strike-slip fault forming the Sibi Re-entrant. InSAR processing of 34 Envisat satellite images showed that the western Sulaiman belt experienced a complex deformation with a mixture of different lateral motions. Satellite mapping of active structures in this region using Landsat 8 and Sentinel 2 images suggested a right-lateral shear zone with evidence of ‘bookshelf faulting’, indicating a distribution of deformation across the zone rather than along a strike-slip fault. The difference is attributed to the shape of the Katawaz basin and the weak detachment sliding over thick sediments.