Item

Abstract

Continental collision at the western boundary of the Indian continent formed the tectonically complex transpressional zones of the Sulaiman Fold and Thrust (SFT) belt. Seismic hazard in the SFT is considered very high due to strong transpressional movement and documented active seismicity. Here, we study SAR time series of Sentinel-1A through LicSBAS to estimate the coseismic crustal deformation along with the inter-seismic, and post-seismic movement caused by the 2021 M 5.9 Harnai earthquake in the central SFT belt. The line-of-sight (LOS) displacement amounts to ~55 and ~65 mm for ascending and descending interferograms respectively, due to thrust-dominated slip over the NW-SE trending fault. We invert the LOS displacement through the Bayesian inversion approach. The inverted InSAR measurements fit well with USGS and ISC model parameters. A simplified fault model shows a dip of 22°, strike of 282°, length of 10 km, and width of 11 km. We perform kinematic inversions to determine the slip on complex fault geometries such as double fault-bend fold (décollement-ramp-décollement) and fault-propagation fold (décollement-ramp) systems. We find post-seismic movement on the fault, however, at this stage, we are not conclusive to interpret the signal as after-slip or viscoelastic relaxation. The double fault-bend structures are commonly observed in the frontal and central SFT zone. Previous work on the frontal zone of SFT indicates the presence of décollement that branches into a shallow ramp (Javed et al. 2022, GRL) matching geological and seismic observations in the SFT belt.