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The study of brittle deformation of the collisional mountains can explain its shallow crustal tectonic evolution and the palaeostress regime. The Main Boundary Thrust (MBT) zone in the western Arunachal Himalaya displays imbrication in the Permian Gondwana sequence between the MBT‐1 (/Bome Thrust/MBT‐Upper) in the north and MBT‐2 (/MBT‐Lower) in the south with consistent northerly dip. The Lower Gondwana rocks occur in the footwall of the MBT‐1 with the Proterozoic Bomdila Group in the hangingwall. The upper Gondwana rocks constitute the hangingwall sequence for the MBT‐2 with Neogene Siwalik rocks in the footwall. This article analyses palaeostress using brittle fractures in the Gondwana rocks that crop out for ~120 km2 in the study area. The fault‐bounded imbricate zone depicts eight brittle shear indicators and four sets of joints (J1 and J2: inclined and J3 and J4: subvertical). The signatures of the inherited pre‐Himalayan extensional deformation are preserved in the Lower Gondwana Miri Formation. The Bichom and Bhareli rocks exhibit brittle deformation features of the Himalayan Orogeny under strong ~N‐S compression. The palaeostress analysis of all joint sets indicates three phases of brittle deformation in the Gondwana and Siwalik rocks of the area. The subvertical joint sets and normal faults in the Miri Formation indicate a north‐northwest (NNW)‐directed extensional phase of the pre‐Himalayan origin. The inclined joint sets of the Bichom and Bhareli formations of the Gondwana sequence depict Himalayan orogeny with ~N‐S compressional phases. The third phase of brittle deformation in the Siwalik sequence depicts an east‐west (~E‐W) extension. The arc‐parallel extension in the frontal fold belt of the Arunachal Himalaya may be due to oblique India‐Asia collisional tectonics. [ABSTRACT FROM AUTHOR]

The W–WNW‐striking Kachchh Mainland Fault (KMF) is the largest intra‐basinal fault in the Kachchh Rift Basin (KRB) located at the western continental margin of the Indian plate, and is responsible for several historic earthquakes, including the 2001 Bhuj earthquake and the 1956 Anjar earthquake. The objective of the study is to constrain the precise location and near‐surface characteristics of the KMF using field and ground penetrating radar (GPR) studies. Efforts were also made to ascertain and map the eastward continuity of the KMF. The fault has a prominent geomorphic expression up to the east of Devisar, where the KMF scarp finally dies out. The KMF marks the lithotectonic contact between Mesozoic rocks in the south and Tertiary rocks in the north. The segmented nature of the KMF has been previously attributed to transverse faults, complex deformation zones and heterogeneous assemblages of unconformable Quaternary deposits. Eight survey sites between Nirona and Sikra were chosen for near‐surface investigation of KMF using GPR. Comparatively, high‐amplitude radar reflections were received from well‐compacted sand‐ and shale‐rich Mesozoic rocks, whereas low‐amplitude weak reflections were observed from softer and clay‐rich Tertiary rocks. In the upper section of the GPR profiles, Quaternary deposits display low‐ to moderate‐amplitude semi‐continuous to wavy reflections. The traceable length of the KMF has been extended eastward by ∼20 km through the current study, which is considered a blind zone as feeble surficial evidence is present, but the fault trace is confirmed near the surface using GPR. The eastern part of the KMF is inferred to be a near‐vertical north‐dipping normal fault based on GPR data analysis. The tendency of the KMF to transform into a reverse fault in the vicinity of the intersection with transverse faults implies zones of relatively higher stress accumulation that might activate and trigger devastating earthquakes in the future. [ABSTRACT FROM AUTHOR]

We highlight scientific blunders in the article published by Mishra et al. (2020). The authors have completely missed the location of Vigodi Fault (VF) along with misidentification of meso-scale structures. The paleostress analysis is based on insufficient field data (14 fault-slip measurements) collected along other faults and results are mutually contradictory, poor quality and highly unreliable. Two domes, not located along the VF are wrongly analyzed. We note that couple of figure captions and some parts of the paper are plagiarized from Vanik et al. (2018) and Biswas (1993). The slip history of VF inferred by Mishra et al. (2020) completely contradicts previously well-established structural facts. We reanalyzed fault-slip data of Mishra et al. (2020) and reached much different results. We conclude that the field data, paleostress analysis and interpretations in the paper by Mishra et al. (2020) are erroneous and do not belong to the VF. [ABSTRACT FROM AUTHOR]

Drainage reorganization on restricted temporal and spatial scales is poorly‐documented. We attempt to decode the relatively complicated mechanism of drainage realignment involving two small rivers that show structurally controlled, highly anomalous channel networks. We provide geomorphic and shallow subsurface evidence using ground‐penetrating radar (GPR) for the presence of a buried paleo‐valley flowing northward through the wind gap and surface faulting along the range bounding Katrol Hill Fault (KHF) which correlates with the previously known three surface faulting events in last ~30 ka bp. Most of the present river channels and the KHF zone are occupied by aeolian miliolite (local name) which is stratigraphic and lithologic equivalent of the Late Quaternary carbonate rich aeolianite deposits occurring in several parts of the globe. The history of drainage evolution in the study area comprises pre‐miliolite, syn‐miliolite and post‐miliolite phases. Geomorphic evidences show that the paleo‐Gangeshwar River flowed north through the wind gap and paleo‐valley, while the short paleo‐Gunawari occupied the saddle zone to the east of Ler dome prior to and during the phase of miliolite deposition which ended by ~40 ka bp. Southward tilting of the Katrol Hill Range (KHR) due to surface faulting cut off the catchment of the paleo‐Gangeshwar River. The abandoned catchment stream extended its channel eastward along the strike through top‐down process while the paleo‐Gunawari River extended its course westward by headward erosion (bottom‐up process). As the channels advanced towards each other they joined to produce the "S"‐shaped bend which formed the capture point. We conclude that multiple surface faulting events along the KHF in the last ~30 ka bp, resulted in uplift and tilting of the KHR which caused drainage realignment by river diversion, beheading and river capture. Our study shows that the complexity of drainage reorganization processes is more explicit on shorter rather than longer timescales. [ABSTRACT FROM AUTHOR]

Highlights • We present detailed fault slip analysis of a previously unmapped E trending fault near Rajula (Gujarat, India). • Total 46 fault slip data (fault plane attitude and slickensides) with three types of striations were analysed for interpreting various slip sense. • Stress ratio of up to 0.2, and a SE trending major stress axis is deduced using T-Tecto software. WinTensor and FaultKin deduced plunging stress axes. • Maximum horizontal stress (σ 1) underwent rotation from offshore to Rajula area showing difference in stress orientation. • The Katar Fault developed under transpressional stress regime induced by the collision and anti-clockwise rotation of the Indian plate. Abstract We analyze paleostress from a region in SW Saurashtra (India) using three free software, T-Tecto, WinTensor and FaultKin based on attitudes of ∼ E-W trending, sub-vertical, brittle fault planes and associated horizontal, inclined and subvertical slickensides, developed over them. We present a detailed fault slip analysis of a previously unmapped E trending fault (herein referred as the Katar Fault) that cuts across and offset the southeastward dipping Deccan lava flows with a dense NE-SW trending dyke swarm belonging to Deccan Trap near Rajula (Gujarat, India). Measured fault strikes do not match exactly with ∼ NW/NNW trending basement structures, deduced by previous geophysical studies, nor with faults reported from the offshore Saurashtra region. However, a few geomorphic features around Katar indicate a similar strike slip offset. A stress ratio of up to 0.2, and a SE maximum principal stress axis were deduced using T-Tecto, while WinTensor and FaultKin gave plunging stress axes. Therefore, stress analyses by T-Tecto seem more plausible. The SH max direction usually remains close to one of the stress axes, and shows up to 36° rotation when compared with the offshore region. We attribute the formation of Katar Fault to post-Deccan Trap oblique slip reverse faulting with sinistral slip due to intraplate transpressional stresses induced by the anticlockwise rotation and collision of the Indian plate with the Eurasian plate at ∼ 55 Ma. This transpressional faulting post-dates the eastward tilting of lava flows and anticlockwise rotation in the dyke swarm patterns caused by the emplacement of large Girnar intrusive body. Detailed structural geological field-work in Saurashtra would be much required to understand its onshore tectonics. [ABSTRACT FROM AUTHOR]