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The intraplate Kachchh Rift basin has been hit by several devastating earthquakes in the historic past including the 1819 Allah Bund Earthquake and the 2001 Bhuj earthquake. The source region of these earthquakes, within the basin have been studied by several workers in the last two decades to understand their potential for earthquake recurrence. However, very little information is available on the palaeoseismic and geomorphic characterization of Kachchh Mainland Fault (KMF). Therefore, in the present study, six trenches were excavated across the KMF, between Lakhpat and Nirona to understand ground deformation pattern and timing of the historic earthquakes. Based on geomorphic and palaeoseismic investigations, five palaeoearthquakes of Early to Late Holocene have been identified between 10,000–890 yrs. Apart from the Holocene, an earthquake of Late Quaternary period was also identified, which possibly occurred around 19,800 yrs BP. Fault related parameters were analyzed to understand the geometry of the active fault scarp along KMF. The results of the analyzed fault geometric parameters show that the vertical displacement along the KMF is higher than the horizontal displacement. The slip rate of the KMF from the western portion to the middle portion decreases from 0.08 to 0.04 mm/yr, and increases towards east from 0.22 mm/yr to 0.36 mm/yr. As the Kachchh district of the Gujarat state is rapidly developing in terms of infrastructural development, the outcome of this research might provide significant inputs for micro zonation studies and also in the evaluation of the seismic hazard in the Kachchh region. [ABSTRACT FROM AUTHOR]

In this paper, we elucidated deformational and kinematic characteristics of the NW-SE trending Vigodi Fault (VF) and its associated subsidiary faults in the western Kachchh basin. We applied paleostress inversion technique to understand the past stress regime from the acquired fault slip data. The subsidiary faults strike NW-SE and NE-SW and slickensided surfaces are well developed on the Fault planes. We present slip analysis and changes in the stress reorientation using the plane solutions to identify the principal stress axis (σ1) position regionally. To obtain Pressure Tension and Null axis (PBT), stress ratio, and principal (σ1) axis we used the right Dihedron Method using the Win-Tensor and T-Tecto software's respectively. Geomorphologically, the VF zone comprises of bedrock strath terraces towards the upthrown block and fill terraces on the downthrown block of the fault. Development of fault scarps, warped Quaternary sediments, slit canyons within Quaternary sediments, river nick-points, and deflected rivers are the major striking features observed along the strike length of the Vigodi Fault. The analyses indicate that NE-SW compressional stress dominates the regional area and the local area is affected by transpressional stress exhibiting oblique slip motion. The combined observations made from the present investigation can be used to estimate seismic hazard and mitigation planning of the study area. [ABSTRACT FROM AUTHOR]

The consequence of strain accumulation along various Himalayan thrusts is manifested in shaping the topography and present day lanscape features of the Himalaya. Consequently, the strain accomodation is attributed to the occurrence of various devastating earthquakes in the Himalayan domain including 1905 Kangra earthquake (Mw 7.8) which occurred along the Kangra valley fault. In the present study, we analyzed and estimatedsss fault related parameters, gradient-length anomaly (GLA) analysis together with Interferometric Synthetic Aperture Radar (In-SAR) measurements to understand the landscape evolution and deformation pattern within the Soan dun (piggy back basin) in the northwest Himalayan front. We combined the results of geodetic, geological, geomorphology and InSAR to constrain the uplift and subsidence between Himalayan Frontal Thrust (HFT) and Main Boundary Thrust (MBT) zones. The estimated results of fault parameters reveal that the horizontal shortening of northwest Himalaya is higher than the vertical uplift. The computed values of GLA magnitude analysis for the uplifted region vary from −9.21 to −0.77, whereas these range from 5.48 to 26.60 for the subsided region. The depicted range of vertical deformation observed from the InSAR measurements ranges from −3.13 to +3.14 mm/y, where the positive and negative value of phases are correlated with the ground uplift and subsidence. The rate of deformation observed from Persistent Scatterer Interferometry (PSI) phase velocity and GLA magnitude is positively supported by the chronologically constrained uplift rates as 3.4 ± 0.3 mm/y. The geomorphic evidences such as folded, tilted and truncated alluvial fan surfaces, offsetting of channels, fault scarps and displaced sedimentary sequences indicate active nature of the Soan dun. The study would be eventually useful for seismic hazard assessment and future infrastructure development in the seismotectonically active regions like Soan dun of NW Himalayan front. [ABSTRACT FROM AUTHOR]

In last 500 years, Kachchh experienced several large magnitude earthquakes (6.0 ≥ M ≤ 7.8), however, not all accompanied surface rupture. The 1819 Allah Bund earthquake (Mw7.8) accompanied surface rupture, whereas, the 2001 Bhuj event (Mw7.6) occurred at a depth of 23 km on E-W striking south dipping thrust fault remained blind. Discontinuities between the denser-brittle basement (?) and overlying ductile-softer Mesozoic-Tertiary-Quaternary succession resulted in a different geometry of faulting. Normal faults associated with rift were reactivated as reverse faults during inversion tectonics, propagated in sedimentary succession and arrested. Thrust-ramps developed along the discontinuities accompanied surface ruptures. Folded structures along the South Wagad Fault (SWF) – an active thrust, exhibits lateral-propagation of fold segments and linkage, suggestive of fault-related-fold growth. Paleoseismic investigations revealed evidence of at least three paleo-earthquakes. Event I occurred before BCE 5080; Event II between BCE 4820 and 2320, and was probably responsible for a massive damage at Dholavira – Harappan site. Event III was between BCE 1230 and 04, most likely caused severe damage to Dholavira. Archaeo-seismological Quality Factor (AQF) of 0.5 suggests that the Dholavira is vulnerable to earthquakes from nearby active faults. With 1500–2000 yr of recurrence interval, occurrence of a large magnitude earthquake on SWF cannot be ruled out. [ABSTRACT FROM AUTHOR]

The present study describes the active tectonic features of the eastern segment of the South Wagad Fault Zone (SWFZ) of the Kachchh Rift Basin (KRB). The SWFZ defines the southern margin of the Wagad uplift with a series of small domes and anticlines forming a low hill range. Geomorphologically, the SWFZ is expressed by the presence of the South Wagad Hill range to the north and the south sloping Samkhiyali and Lakadia plains to the south. The easternmost part of the SWFZ consists of domes and anticlines having a rugged topography, which comprises of Mesozoic to Neogene rocks and is practically unexplored as far as their active tectonic characterizations are concerned. The geomorphic expression of the SWFZ in the eastern segment consists of the Gagodar, Kanmer, Guan and Mardak domes and anticlines. They are exposed as a series of linear mounts projected amidst the Little Rann of Kachchh and surrounded by the alluvial sediments of easterly flowing rivers as well as the Rann sediments. The active nature of the eastern SWFZ is portrayed by warping, flexuring, alluvial fans, tilted Quaternary deposits, scarps, gullied surfaces, slickensides and knickpoints. Presence of wave cut cliff and notches at Mardak Bet suggests that the eastern segment of SWFZ is marginally uplifted during Middle to Late Holocene period. We provided a detailed morphotectonic map of the eastern segment of SWFZ, which can be used for future infrastructural development, town planning and seismic hazard assessment in the region. Further, the study suggests that the seismically silent eastern segment of the active SWFZ is capable of generating a large magnitude earthquake similar to the 2001 Bhuj earthquake or the 1819 Allah Bund earthquake in the future, owing to long-term stress accumulation. [ABSTRACT FROM AUTHOR]

In the present study, an attempt has been made to delineate anomalous morphotectonic elements in the lower valley of Ravi and Beas rivers of the NW Himalaya by utilising the digital elevation model (DEM) as well as GIS based approach. We selected the surrounding areas of both the rivers as these have developed tectonically formed lakes such as Khajjiar and Rewalsar in late Holocene and lie in the north and south of Kangra re-entrant structure. We generated topographic swath profiles, calculated normalized steepness index (ksn) and hypsometric integral (HI) and conducted lineament analysis and finally correlated the obtained data set with the contemporaneous seismicity to decode the tectonic activity in the region. Based on the calculated HI for both the areas as 0.45 and 0.47, we infer that there are anomalous changes in the steepness, pointing to the presence of active tectonics. By using lineament analysis, geological information and the quantitative analysis, we identified lineaments parallel and oblique to the regional strike of the NW Himalaya, indicating the area as tectonically active. The lower steepness values along the inferred lineaments suggest the presence of strike-slip features that absorb the oblique convergence of the Indian plate with Eurasia. The GPS based additional observations suggest significant amount of deformation, showing higher deformation rate in the vicinity of the Khajjiar as compared to the Rewalsar locality. Based on remote sensing and GIS based approaches, we conclude that the study area is tectonically very active, hence there is need of careful examination of identified structures and impact on the development of infrastructure and seismic hazard assessment of the western Himalaya. [Display omitted] • Pull apart Sundernagar basin and Rewalsar lake were studied. • KJR exhibits higher steepness than the RWL. • Lithology does not affect steepnessand HI distribution locally. • Lineaments with seismicity supports their tectonic nature. [ABSTRACT FROM AUTHOR]