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In the northwest Himalayan region, the ongoing out-of-sequence deformation caused emergence of Back Thrust (BT) around 43ka, which attributed the growth of anticlines parallel to the strike of major thrusts. This spatial and temporal geomorphic deformation is accompanied by coexisting river incision in the axial zone of anticlines and base-level fall along with upstream migration of knickpoints in the longitudinal river course. We used the Stream Power Incision model (SPIM) which relates the normalized steepness index (k sn), and concavity index (θ ref) with the slope (S) of longitudinal river profile as a power-law function of upstream area (A). and estimated these parameters for Beas, Soan, and Sutlej rivers to decipher the spatial distribution of deformation pattern. Using SRTM DEM and based on strike parallel variations of the k sn we identified segmented nature of the NW Himalayan thrusts. Further, the dynamics of river basins and transience along the tributaries and main stem rivers has been analyzed by Chi analysis (χ), which is attributed to geometric disequilibrium of the rivers. The results of k sn and χ analysis together suggests that the crustal shortening of NW Himalaya is caused by segmental reactivation of the thrusts. Further, investigating the change in steepness along longitudinal course aids in understanding the differential uplifts patterns in actively deforming segments of major NW Himalayan thrusts. [ABSTRACT FROM AUTHOR]

The Sabarmati River basin, Gujarat State, western India is one of the major river basins of Gujarat State, playing host to major cities such as Ahmedabad and Gandhinagar, both of which are important economic and political capitals of Gujarat State. In the study reported here, we collected available information on the Sabarmati River basin, Gujarat State in terms of geology, tectonics, seismicity, and shear-wave velocity and assimilated and integrated this information into a geographical information system (GIS) platform to generate a rapid first-order seismic hazard map of the area. The integration of different criteria, such as peak ground acceleration, amplification factor, geology and geomorphology, liquefaction, and seismotectonics critical to seismic hazard, was performed following pair-wise comparison using the analytical hierarchy process, wherein each thematic map was assigned a weight on a 1 to 5 scale depending on its contribution to the seismic hazard. Seismic hazard was evaluated using a numerical rating scheme with the help of the GIS. Analysis of the generated map revealed that the seismic hazard is highest in the southeastern part of the area, moderate in the central part, and lowest in the northeastern part comprising the Aravalli Range. The seismic hazard map also shows that almost 40% of the study area, namely that comprising basins of the Sabarmati River and its tributaries, is prone to high seismic hazard. Our results show that it is possible to generate a macro-level seismic hazard map by integrating available information and that this map is a useful tool for urban planners and helps in zeroing in on the areas where seismic microzonation or site-specific studies are required. [ABSTRACT FROM AUTHOR]

Rana and Sharma (2017) dispute our tectonic interpretation mainly on the basis of what they believe (climate?). However, we welcome their comments, as this gives us a chance to highlight the ambiguity inherent in discriminating the climate-tectonic imprints in morphotectonic records that are prevalent in current research. We should note that the paper published by Kothyari et al. (2017) was reviewed by national/international reviewers. We would like to emphasize the fact that the paper does not rule out the role of climate. However, most importantly, it presents significant features and observations that collection/assemblage points toward the dominant role of tectonics in their shaping, and not solely climate, as postulated by Rana and Sharma (2017). The objective of this paper is to identify tectonic signatures (geomorphology) in a monsoon - dominated, tectonically active terrain like the North Almora Thrust (NAT). These faults are marked by previous workers based on field evidence such as folding and faulting of lithological units; presence of slickensides parallel to the fault; offset of NAT owing to a transverse fault; and offset of drainage, drainage basin analysis, strath terraces, fluviolacustrine terraces, development of scarp, narrow river course, and deeply incised valleys. However, we disagree with the comments raised by Rana and Sharma (2017), because they are highly skewed toward the climate school of thought, and did not perceive the setting as a collection of landforms. Instead, they attempted to view them in isolation. Because these comments are important, we will try to further our research incorporating issues related to isolation of climate and tectonics imprints in the immediate future. We would like to thank Rana and Sharma (2017) for raising some basic questions on our work as this gave us an excellent opportunity to summarize and present the dominance of various processes and related landforms as earlier reported by Kothyari et al. (2017). A point-by-point detailed rebuttal/explanation of their queries is provided below. [ABSTRACT FROM AUTHOR]

An earthquake of 2006 Mw 5.7 occurred along east–west trending Gedi Fault (GF) to the north of the Kachchh rift basin in western India which had the epicenter in the Wagad upland, which is approximately 60 km northeast of the 2001 Mw 7.7 earthquake site (or epicenter). Development of an active fault scarp, shifting of a river channel, offsetting of streams and uplift of the ground indicate that the terrain is undergoing active deformation. Based on detailed field investigations, three major faults that control uplifts have been identified in the GF zone. These uplifts were developed in a step-over zone of the GF, and formed due to compressive force generated by left-lateral motion within the segmented blocks. In the present research, a terrace sequence along the north flowing Karaswali river in a tectonically active GF zone has been investigated. Reconstructions based on geomorphology and terrace stratigraphy supported by optical chronology suggest that the fluvial aggradation in the Wagad area was initiated during the strengthening (at ~ 8 ka) and declining (~ 4 ka) of the Indian Summer Monsoon (ISM). The presence of younger valley fill sediments which are dated ~ 1 ka is ascribed to a short lived phase of renewed strengthening of ISM before present day aridity. Based on terrace morphology two major phases of enhanced uplift have been estimated. The older uplift event dated to 8 ka is represented by the Tertiary bedrock surfaces which accommodated the onset of valley-fill aggradation. The younger event of enhanced uplift dated to 4 ka was responsible for the incision of the older valley fill sediments and the Tertiary bedrock. These ages suggest that the average rate of uplift ranges from 0.3 to 1.1 mm/yr during the last 9 ka implying active nature of the area. [ABSTRACT FROM AUTHOR]

In present study the results of integrated studies of landform development and geomorphic indices of drainage networks across the South Wagad Fault (SWF) zone have been presented. The SWF is a structure that is morphogenic in nature, creating a 40-m-high E–W trending escarpment that extends ~ 80 km at the southern end of the Wagad uplift. The SWF got reactivated during the Bhuj earthquake of 2001, continued aftershock activity of M ≥ 4 levels were recorded in the epicentral zone, north of the Kachchh Mainland Fault and west of the SWF. Strath terraces along the river valleys and the truncation of alluvial fans along the mountain front, incision, and offset of rivers suggests an active nature of the SWF. To assess the relative tectonic activity, morphometric indices such as stream-gradient ( SL ) index, hypsometric integral ( HI ), basin asymmetry ( AF ), mountain front sinuosity ( S mf ) index, sinuosity index ( SI ), and basin shape ( B S ) have been analyzed. The landform development along the river valley in the SWF zone suggests reactivation of the SWF between 12 and 3 ka. The southern front of Wagad is found to be uplifting at the rate of 2.8 mm/y during the last 12 ka as estimated through OSL dates. The relative index of active tectonics (RIAT) by the study of different geomorphic parameters and field checks indicates that most of the Wagad highland is active. The compressional strain of 0.05 μstrain/y inferred from the GPS study in the SWF area attests to the activeness. [ABSTRACT FROM AUTHOR]

Geomorphic and morphotectonic evaluations of the Kashmir Basin have been carried by implicating different geomorphic indices such as stream-gradient index (SL), hypsometric integral (HI), drainage basin asymmetry (AF), valley floor height and width ratio (Vf), transverse topographic symmetry factor (T), mountain front sinuosity (Smf), drainage basin shape (BS) and sinuosity index (SI) for the categorization of relative index of active tectonics (RIAT) through the use of geographic information systems (GIS) so as to decipher the role of neotectonics in geomorphologic evolution of the basin. The verified RIAT classes through field investigation and validation reveal the traverse of twenty-one active faults in the basin with demarcation of three RIAT classes viz., class-1 (inactive 20.07% of the area), class-2 (moderately active; 36.52% of the area) and class-3 (very active; 43.4% of the area). The observed values of RIAT distribution pattern are well corroborated with field observations. Ultimately, the overall geomorphic outputs and clustering of recent seismicity support the active tectonic control over the Kashmir basin, India. [ABSTRACT FROM AUTHOR]

Records from the Tangtse Valley in the Trans-Himalaya reveal depositional history since 48 ka, with fluvial aggradation followed by incision, lacustrine sediment fill, and later incision. Varied sedimentary architecture with fluvial episodes intervened by lacustrine pulses, flood events, colluvial and glacial activity are preserved. The valley is located west of the Pangong Tso/Bangong Co, one of the largest lakes in Tibet which has served as a spillway, flooding and damming the entire Tangtse Valley, resulting in the formation of a lake. Today Pangong Tso consists of five basins separated by shallow sills and is fed by snow melt. Documentation based on 14 C and OSL chronologies of the sediment sections throughout the valley reveals evidence of a sixth basin of Pangong Tso toward west, occupying the present day Tangtse Valley between 9.6–5.1 ka. This event coincides with periods of high lake levels in Tibet, China as well as intensified monsoon periods over the Indian subcontinent. A fluvial regime around 48 ka and 30–21 ka with comparatively arid conditions and dry phases interspersed by flooding is documented. The valley has been incised to depths of 40–50 m in the upper part and to 130 m in the lower part. The incision rate ranges from 0.3 to 1.2 mm yr − 1 in the upper part and reaches as high as 10.8 mm yr − 1 in the lower valley. Much of the incision took place between 22 and 9.6 ka although repeated sediment fill-incision cycles in the valley from 30–22 ka, 22–9.6 ka, 9.6–5.1 ka, 5.1 ka, and even to present time were observed. [ABSTRACT FROM AUTHOR]

The Saurashtra peninsula, a Deccan Trap terrain, in western India lacks the studies that document on-land information of tectonically active faults. In the present paper, the tectonogeomorphology of the Shetrunji River basin is investigated to identify the neotectonic signatures of the buried structural element by detailed analyses of the landforms and drainage pattern using quantitative geomorphic analysis, morphostructural studies and Gradient length analysis (GLA) along with field investigation. The basin has been divided into three segments based on channel orientation, (a) Segment-1 (upper reach): oriented in NE-SW direction (b) Segment-2 (middle reach): oriented in an E-W direction and (c) Segment-3 (lower reach): oriented in NW-SE direction. The tectono-geomorphic analysis suggests the neotectonic deformation is mainly demonstrated by the NE-SW oriented Girnar Fault (GF) in Segment-1 and E-W oriented Shetrunji Fault (SF) in Segment-2. The Segment-3 interestingly shows least or no tectonic deformation signatures. For the first time, we report the geomorphic evidence of the two main faults 1) the Girnar Fault (GF) ~ a left-lateral strike slip fault and 2) the Shetrunji Fault zone (SFz) ~ a right-lateral strike slip fault. The interplay between drainage pattern and buried structures are observed in the form of offset channel/offset ridges, deflection in stream and linear valleys. The SFz is characterized by an anastomosing drainage pattern, offsetting/deflection of streams and development of linear valleys in zone which is 52 km in length and 2 km wide. The SL index and K sn show high values along the fault zone, which is also, supported by the presence of incised river channel, entrenched mender and incised ravine surfaces. The study reveals the prevalent neotectonic activity in the Shetrunji River basin along with the GF and the SFz. The findings are consistent with the geomorphic - structural setup of the region, and coincide with the historical as well as current seismicity distribution. [ABSTRACT FROM AUTHOR]