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In the present study, we assess seismic hazard potential and surface deformation pattern along and across the strike of major active faults in the intra-plate Kachchh Rift Basin (KRB). Towards this, we adopted river Gradient Length Anomaly (GLA) technique, which detects recent tectonic deformation along a river profile on local and regional scales. The major deviations along the river profile can be correlated with exogenic (erosion/sedimentation/anthropogenic) and endogenic (active tectonic movement) processes. We analysed 130 river profiles for GL anomalies, over an area of ~26,700 km2 in the KRB to identify possible locations that have undergone active tectonic deformation associated with the fault movement. The acquired results show that the higher magnitude negative GL anomalies (uplift) are observed proximal to the fault zones. Our estimates reveal that, around 13% of the study area falls under high tectonically active zone, around 27% of the area falls under moderately active zone, while 60% of the area shows very low or negligible tectonic activity. The estimated results of the GL anomalies are compared with the existing double-difference tomograms, to understand the role of subsurface fault dynamics on the GL anomalies. Furthermore, the results of GLA are correlated with the existing results of the peak ground acceleration (PGA) values of the basin, in order to obtain the precise information regarding surface deformation and site-specific ground acceleration for accurate assessment of seismic hazard. [ABSTRACT FROM AUTHOR]

We present geodetically estimated crustal strain rates in Uttarakhand Himalaya, a region which has long been considered as a part of seismic gap. We processed and analyzed the GPS data, acquired from the sites enveloping all the litho-tectonic units from the Sub Himalaya in the south to the Tethys Himalaya in the north together with the major Himalayan thrust/fault systems. On the basis of the obtained dataset, we conclude that the maximum amount of crustal shortening takes place towards the hinterland in the vicinity of Main Central Thrust and Inner Lesser Himalaya which is also in agreement with high seismic activity in these sectors. The GPS velocities of the sites (Indian reference frame) show significant variation from the sub-Himalaya to the Tethys Himalaya. The Sub and Inner Lesser Himalayan parts exhibit low deformation rate in contrast to the maximum amount of deformation in the Inner Lesser and Higher Himalayan segments. The strain analysis reveals lateral variation with high strain zones (HSZ) and moderate strain zones (MSZ) within the compressional regime in the Uttarakhand Himalaya. The strain rate of 0.45 and 0.25 micro-strain/year is observed in the HSZ and MSZ respectively. By comparing the strain rate with the seismicity pattern for the past five decades, we suggest that the earthquakes in the HSZ are related with ramp structure of the MHT, whereas, part of accumulated strain in the MSZ is being released in form of the present day seismic activity. [ABSTRACT FROM AUTHOR]

Himalaya is one of the youngest mountain systems with a fragile ecosystem due to continued collision tectonics. The endogenic and exogenic processes in the Himalaya have made landslide one of the critical surface processes continually sculpting the Himalaya. Constituting the hanging wall of the Main Boundary Thrust (MBT), the south-facing slope of the Mussoorie Syncline is prone to various slope movements. Several old and active landslides are taking place along the Dehradun-Bhitarli Chhoti-Mussoorie road section. The main causative factors for landslides are tectonics, slopes, and human interference. The highly sheared bedrocks and high numbers of joint sets in the bedrocks are the signatures of the successive phases of tectonic uplift along the MBT imprinted on the bedrocks. The intersecting joint sets developed in the bedrocks have formed wedges, and these wedges have facilitated the recurrence of several landslides. Wedge failure, sliding (bedrock and debris), and toppling are the primary types of failure mechanisms, of which wedge failure-induced landslides accounts for the maximum. The south-facing slopes are very steep and are also one of the contributing factors to the instability of the hill slope. Anthropogenic activities have further aggravated slope stability as the roads are constructed across steep slopes and highly sheared rocks. The onslaught of rains easily destabilizes the weak rocks during monsoon, where the region receives a good amount of rainfall. The landslides occur primarily during or right after monsoon when the slope-forming materials become saturated with water. Recent tectonic activity along the MBT is evident from tectonic landforms such are uplifted terraces, linear fault traces along the MBT, and triangular facet cones. [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]

The morphotectonic elements of the Baijnath Klippe (BK) have been examined to understand the kinematics of the Inner Kumaun Lesser Himalaya from Tertiary to Late Quaternary. The BK is bounded by two thrusts: the Askot Thrust (AT), to the north and the Baijnath Thrust (BjT), to the south. The older (20 Ma) hanging wall rocks (mylonites and phyllites) are underlain and surrounded by quartzites (equivalent to Nagthat Formation of Outer Lesser Himalaya). The kinematics study and strain analysis along Dewal–Narayanbagarh transect provides the varied intensity of deformation (D1, D2, and D3) within the zone of BK. The D1 event is characterized by isoclinal tight folds in phyllite and mylonite; the D2 phase is characterized by open folding in mylonite. However, the youngest event D3 phase is observed as a regional synclinal folding of BK and associated rocks. The presence of 1–3-km-thick mylonite zone parallel to the thrust planes is related to the compressional event of Miocene age. The geomorphic pattern and chronologically constraints (OSL ages) with spatial variability in the incision/uplift rate suggests that the terrain is undergoing differential crustal deformation during Late Quaternary. Kinematic indicators such as streaky foliations, S–C foliation, mantled porphyroclasts, micro-shears with bookshelf gliding, and mica fish found in mylonites (macroscopic as well as microscopic) indicate ductile deformation in the area. We used Flinn plot (Rf/ϕ) and Fry (Tectonophysics 60:89–105, 1979) analysis to delineate the finite strain pattern in 21 oriented samples collected across the BK bound thrusts (BjT and AT). The strain analysis revealed an increasing trend of strained quartz grains, which presents triaxialoblate strain geometry (flattening i.e., 0 < k < 1) towards the structural discontinuity. The textural (chessboard, myrmekite, undulose extinction and fracturing in quartz and feldspar) and mineralogical properties (non-flaky) of quartz and feldspar indicate the temperature of deformation and mylonitization ranging 300–500 °C. [ABSTRACT FROM AUTHOR]

Magnetotelluric (MT) data have been acquired at 40 locations in Tuwa and its surrounding region (200 km east of Ahmedabad and 15 km north-northwest of Godhra) in the Mainland Gujarat with an average station spacing of 1.5 km. MT impedance tensors have been estimated in the period range of 0.001-100 s. The data have been modeled using non-linear conjugate gradient scheme taking both apparent resistivity and phase into account. From the 2D models of the MT data, the weathered granite with Quaternary sediments (with resistivity of < 700 Ω m) have been inferred up to a depth of 500 m followed by Godhra granite (having resistivity up to 105 Ω m) with a thickness 6.5 km. The Aravalli supergroup has been inferred below Godhra granite. The Lunavada group of rocks have been inferred in the eastern part of the study area (having resistivity value ranging from 103 to 104 Ω m) separated from the Godhra granite by a contact zone. The comparatively very low-resistivity rocks (< 400 Ω m) of Udaipur formation followed by Paleoproterozoic carbonate rocks with fluid have been inferred below 8-10 km depth. The percolation of water from the surface through the contact zone of Lunavada and Champaner groups has been suggested. The presence of hot water springs in 10 km SW from the center of the study area (at the contact zone of Godhra granite and basalt) might be due to the western trending lithostratigraphic slope, hydrostatic pressure generated due to heat produced from interaction of water with the carbonate rocks at deeper depth and high subsurface temperature due to high geothermal gradient. The segmented nature of Himmatnagar Fault (HnF) is identified in the central portion of the study area. [ABSTRACT FROM AUTHOR]