Search

The key objective of the present study is to estimate the surface displacement and to understand/monitor the active deformation pattern in the Kachchh region post the 2001 Bhuj Earthquake by implementing the Persistent Scatterer Interferometric Synthetic Aperture Radar (PSI) and Differential Interferometric Synthetic Aperture Radar (DInSAR) techniques. We employed the ENVISAT ASAR (15 images), ALOS PALSAR (6 pairs) and SENTINEL-1A (117 images) data sets acquired during the periods 2003–2005, 2007–2009, and 2016–2020 respectively. The PSI results of the Envisat dataset reveals that the Kachchh mainland region has undergone an average surface deformation of ± 22 mm/yr during 2003–2005. The maximum displacement observed from the ALOS PALSAR data sets (Window-1 to 6) during the period 2007–2009 is ∼ ± 1.2 cm. Further, the ground displacement observed from the Sentinel-1A dataset during the period 2016–2020 is ±16 mm/yr for the west-central region and 6 mm/yr uplift and 8 mm/yr subsidence in the eastern Kachchh mainland region. Surprisingly, high rate of deformation is detected towards the Pachham Island, Banni, Rann and the eastern region of the Kachchh after the 2001 Bhuj event. Correlating the results of different data sets, it is concluded that the deformation is high near the vicinity of the fault zones indicating the tectonically active nature of the faults. From the obtained results, we infer that, post the 2001 Bhuj earthquake, the surface displacement in the Kachchh mainland region is escalated till 2009 which is due to continuous aftershock activity and then started declining because of the ongoing seismic settlement. The acquired deformation rates are correlating well with the GPS derived displacement rates. Further, our results will assist in accurately demarcating the extent of the fault zones and also helps in precisely marking the areas undergoing active deformation, which will aid in micro zonation studies, mitigation planning and also for the preparation of an active tectonic map for the region. [ABSTRACT FROM AUTHOR]

The present study area represents one of the active segments of the frontal part of the Arunachal Himalaya. The major structural boundaries traversing the area are the Main Boundary Thrust (MBT) and the Himalayan Frontal Thrust (HFT) and other local faults are tectonically active, as evident from the landforms that evolved in the fault zones. Strath terraces and uplift fluvial terraces are observed in the hanging‐wall block of the HFT and MBT, and along the HFT straight to curvilinear mountain fronts are observed. Normal faults both transverse and parallel to the strike of HFT are observed in the hanging‐wall block of the HFT. West of Pasighat the sub‐Himalaya terrain resembles a duplex, where there is gradual rise in elevation from the Brahmaputra Plain to the low‐lying hills of the sub‐Himalayan and sudden rise in elevation across the MBT. Drainage aligning to the bedrock structures and stream migrations are observed in the fault zones. Along the MBT, the sub‐Himalayan rocks are thrusted over either by quartzite or black carbonaceous shales, in some sections the MBT is behaving as a back‐thrust that dips towards the south. The MBT has also been displaced by almost N–S‐trending transverse faults where highly sheared bedrocks are also observed. Tilting of Quaternary fluvial deposits are observed in the hanging‐wall blocks of intraformational thrusts at two locations. Signatures of paleoseismic activities in the form of various soft‐sediment deformational structures are observed in Quaternary deposits in the HFT zone and also in the hanging‐wall block of the MBT. To determine the deformation and strain rate accumulation, we have re‐analysed the available GNSS results of the area, which indicate a deformation rate of up to 16 mm/year in the vicinity of the Pasighat region. The GPS‐derived deformation rates are well corroborated with the existing results of peak ground acceleration (PGA) anomalies. The component–wise motion indicates higher fault perpendicular motion in this part, which reveals an accumulation of more strain along the major Himalayan faults. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Island Belt Fault Zone (IBFZ) records multiphase deformation events. • The IBFZ of Pachham and Khadir uplift demark distinctive stress patterns and zones. • Crosscutting relationship of faults defines the superposition of stress in the IBFZ. • Reconstructing paleostress data determine four major tectonic events in the IBFZ. The Kutch Rift Basin (KRB) is a paleorift basin formed during the Gondwana breakup between the Indian and African plates that involved multiple deformational events. The present study demarks paleostresses induced during these deformational phases using paleostress inversion method and reconstructed the tectonic evolution of the Island Belt Fault Zone (IBFZ) situated in the Island Belt Uplift (IBU) (Pachham, Khadir, Bela and Chorar Uplift) in the northern KRB. The IBFZ comprises several faults, from which 145 distinct fault-slip data were used for paleostress analysis. In addition, the geometry of the cross-cutting fault planes and their induced paleostresses were correlated to reconstruct the relative timing of the deformational events in the IBFZ. The results were further associated with the known global events and with data from the literature to form an evolutionary model of the IBFZ. The present research determines paleostress induced during four major deformational events in the IBFZ region as: (a) extensional rifting phase followed by a transitional transtensional phase, (b) rift failure and compressional phase during basin inversion, (c) transitional transpressional phase, and (d) the Reunion hotspot magmatic and compressional phase during India-Eurasia collision. [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]

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]

The focus of the present study is to estimate the active surface deformation/displacement affecting the landscape of the eastern Kachchh basin with a particular emphasis on the Wagad, Khadir Island, Bela Island, Chorar Island, and adjoining regions by implementing Differential Interferometry Synthetic Aperture Radar (DInSAR) technique using ENVISAT and SENTINEL-1A radar imagery. To evaluate the deformation pattern using DInSAR, we used ENVISAT-ASAR 2003 to 2005 and 2006 to 2009 data products and SENTINEL-1A data set of 2018–2020. The cumulative displacement of 0.2–0.3 cm for the period of 2003–2005 and 0.19–0.22 cm for the period of 2006–2009 has been observed for the South Wagad Fault region. Similarly, the results acquired from SENTINEL-1A data set revealed a cumulative displacement of 0.16–0.18 cm for the period of 2018–2020. The Island Belt Fault zone shows 0.27 cm displacement, while it is 0.10–0.17 cm for the Gedi Fault zone. The rate of deformation estimated from the present study is well corroborated with the existing results of GPS driven uplift rates. The combined results of DInSAR and GPS indicate that the northern part of the Wagad region is deforming much faster than the south Wagad region. The displacement detected to the east of the epicentral zone of the 2001 Bhuj earthquake indicates the presence of a zone of weaker structures, which may trigger a large magnitude earthquake in the future. Our estimated results of the short-term ground displacement are well corroborated with the existing geological information. This ground displacement is attributed to the tectonic subsidence towards the eastern part of the South Wagad Fault region and within the wide zone of the Island Belt Fault and Gedi Fault zones. The areas with a high amount of displacement have experienced continuous seismicity during the last two decades in the Eastern Kachchh region and might encounter moderate to high seismicity in the near future. The results also provide a better understanding of the active surface deformation pattern taking place in the seismically sensitive eastern Kachchh region. [ABSTRACT FROM AUTHOR]