Magnetic fabric and geomorphic characteristic of Neotectonic activity along strike direction of North Almora Thrust,Kumaun Lesser Himalaya,India

Structurally,the North Almora Thrust(NAT),is placed in the northern proximity of the Almora Nappe(AN)in the Kumaun Lesser Himalaya.The NAT is characterized by the presence of a zone of mylonitic rocks of basal Saryu Formation(1800±100 Ma)in the hanging wall and the metasedimentaries of Inner Lesser Himalayan rocks as the footwall block.The NAT has been dextrally offset by two estabilished maj or faults i.e.Saryu River Fault(SRF)in Saryu Valley and Dwarahat-Chaukhutia Fault(DCF)in Ramganga valley.In present study,we identified four new faults,based on field study,geomorphic landform and magnetic fabric analysis.These faults are N-S trending Pancheshwar Fault,NE-SW Rameshwer Fault,NNE-SSW trending Kosi Fault,and NNE-SSW trending Gagas Fault(GF).Our results show that the zone is bound by cross cutting relation with NAT and these fault zones are comparatively more active than other regions.Furthermore,we suggest that the steep and NW-SE orientation of magnetic foliation within the NAT zone is a result of NE-SW oriented progressive regional compression.The magnetic foliations represent the unseen internal foliations in the rocks developed due to preferred alignment of magnetic minerals and can be found through the Anisotropy of magnetic susceptibility(AMS)study.Variation in the alignment of the field and magnetic foliations are developed due to superimposed brittle deformation along the faults over the pre-existing field foliations.Magnetic foliations represent the impact of last stage deformation and significant to find brittle deformation and finite strain in the rocks of the study area.The lowering of anisotropy(Pj)away from the fault zone represents distribution of strain across the NAT zone.AMS fabric confirms the presence of faults developed across the NAT zone and also explains the deformation pattern along these faults.The geomorphic anomalies and steepness changes across the NAT zone are correlated with active deformation along the NAT and associated transverse faults.

Response of drainage to tectonics and PS-InSAR derived deformation study in Bilaspur,northwestern Himalaya,India

The study of drainage patterns in tectonically active regions is conducive to the prediction of regional geomorphology.Subtle subsurface changes can be detected by drainage conditions and manifested in the form of drainage anomalies.The Satluj valley of Bilaspur,which is traversed by numerous faults in northwest Himalayan region,was selected to analyze the effect of active tectonics on drainage evolution.With the Persistent Scatterer Interferometric Synthetic Aperture Radar(PS-InSAR)technique,SENTINEL-1A data were used to estimate the active surface deformation between September 2015 and December 2020.The results show that the region between Barasar Thrust(BrT)and Main Central Thrust(MCT)is undergoing deformation of±12 mm/yr.The Stream Power Incision Model(SPIM)was used to predict deformation patterns.To validate the tectonic activity generated by the drainage network,seismic bvalues were calculated,indicating the accumulating stresses.This study shows the importance of drainage anomalies in tectonically active areas.When used in close combination with other seismotectonic parameters,drainage anomalies can be effective in delineating tectonically active regions.