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The active tectonic aspects of the Indo-Myanmar Range (IMR) have not yet been studied in detail in spite of the fact that it's seismically active. In the present study qualitative and quantitative geomorphic analyses have been carried out to understand the active tectonic evolution of Nungba, and Barak- Makru thrust sheets (NBTS and BMTS) in the central part of IMR. The focus of the study is on understanding the active spatial growth pattern of adjacent thrust sheets in an evolving mountain range and providing baseline data for further detailed seismotectonic and seismic hazard vulnerability analyses. Drainage characteristics, disposition of landforms and statistical analyses of Normalized Steepness Index (ksn), Hypsometric Integral (HI) and Transverse Topography Symmetry Factor (T), computed for a total of 164 4th-order drainage basins, reveal that both of these adjoining thrust sheets are actively uplifting. Higher values of ksn (mode = 111) and HI (mode = 0.46) in NBTS suggest its faster uplift than the BMTS, which has comparatively lower values of ksn (mode = 56) and HI (mode = 0.43). Moreover, the northern parts of the both the thrust sheets are uplifting faster than their southern parts due to along-strike variations in the movement on their basal thrusts, as a result of which the NBTS has been south-southeastwardly down-tilting and the BMTS is south-southwestwardly down-tilting. The study reveals that both the adjacently lying NBTS and BMTS have almost the same spatial growth patterns that are mainly controlled by the movements on their basal thrusts. [ABSTRACT FROM AUTHOR]

The NE–SW trending and SE dipping Thoubal‐Chandel Thrust (TCT) in eastern Manipur Hills of the Indo‐Myanmar Range (IMR) places the Thoubal‐Chandel thrust sheet over the Churachandpur‐Mao thrust sheet. Despite being seismically active, the active tectonic aspects of the major structural discontinuities within the IMR, including TCT, are not yet studied in detail. The present study aims to examine the active tectonics of the TCT and other associated faults, with particular focus on deformation of the Churachandpur‐Mao, and Thoubal‐Chandel thrust sheets. Association and disposition of landforms, and statistical analyses of Mountain‐front Sinuosity Index (Smf), Stream Length‐Gradient Index (SL), Hypsometric Integral (HI), Drainage Basin Asymmetry Factor, and Transverse Topography Symmetry Factor (T) reveal that both of these adjacently lying thrust sheets are actively uplifting due to oblique‐slip movement on their basal thrusts, but with spatially variable rates. In general, higher SL (mode = 219) and HI (mode = 0.527) in large parts suggest faster uplift of the Thoubal‐Chandel thrust sheet than the Churachandpur‐Moa thrust sheet, which has comparatively lower SL (Mode = 140) and HI (mode = 0.416). However, differential along‐strike uplift rates have caused tilting of both the thrust sheets. Faster uplift of the northern part of Thoubal‐Chandel thrust sheet has caused its overall southward down‐tilting, whereas faster uplift of the southern part of Churachandpur‐Mao thrust sheet has caused its overall northward down‐tilting. The study brings out that the deformation pattern of even the adjacent thrust sheets of growing orogens could be at stark variance albeit the same stress regime. [ABSTRACT FROM AUTHOR]

The Churachandpur-Mao thrust (CMT) in Indo-Myanmar Range (IMR) is known to be tectonically active, but nevertheless the extent and pattern of activities on it and effects thereof on the surrounding region has not been determined as yet. We herein present the results of our tectonic geomorphological investigations on these aspects across a long stretch of CMT zone spanning western Imphal intermontane valley and enclosing frontal mountains. The NNE-SSW trending CMT and NW-SE trending Sekmai fault have subdivided the area into four tectonic blocks. Geomorphic features in conjunction with statistically analyzed Mountain-front Sinuosity Index (Smf), Stream Length-Gradient Index (SL), Hypsometric Integral (HI), Drainage Basin Asymmetry factor (AF), and Transverse Topography Symmetry Factor (T) reveal variations in nature and extent of tectonic activities, and thus the pattern of surface deformation in these tectonic blocks. Tectonic blocks to the north of Sekmai fault are experiencing more intense activities than the tectonic blocks to the south of Sekmai fault. North of the Sekmai fault, the CMT's footwall is experiencing the most intense activity and thus severe surface deformation in the area, whereas the tectonic activity in the CMT's hanging wall here is only intense in the northern part. To the south of Sekmai fault, while the hanging wall of the CMT is experiencing relatively moderate tectonic activities, the footwall of the CMT is experiencing moderate to intense tectonic activities in different parts, being most intense close to the Sekmai fault. Tectonic activities have caused an overall southward down-tilting of the CMT's footwall to the north of Sekmai fault, and overall northward down-tilting of the remaining three tectonic blocks. Evidently, the tectonic activities and thus the pattern of active surface deformation in the CMT zone of the area is significantly influenced by the transverse Sekmai fault. [ABSTRACT FROM AUTHOR]