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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]

Mishra et al. (2020) are thankful to Maurya et al. (2021) for raising some basic questions on their work, as it gave the authors an excellent opportunity to validate and support their claim. Maurya et al. (2021) have to understand that Vigodi is a ~ 5–7 km wide fault zone including Vigodi-Gugriana-Khirasra fault complex, where several NW-SE to NNW-SSE striking faults are clearly visible (for details, refer to Fig. 2 of Mishra et al., 2020). Further, Mishra et al. (2020) would like to emphasize that they have worked on only one segment of the Vigodi Fault (where they encountered classical evidence of faulting) located between Vigodi and Dayapar and presented the structural data for the same. As specified earlier, Mishra et al. (2020) worked on a branch of the Vigodi Fault zone, and the data collected by them is sufficient for analyzing only a small area. Maurya et al. (2021) have stated that " Two domes, not located along the VF are wrongly analysed ". Here Mishra et al. (2020) would like to emphasize that both the domes are associated with the western branch of the VF zone. In Biswas (1993; Pg. no. 323) these two domes fall under the Vigodi Fault zone (amongst the series of domes on the upthrust part of VF). [ABSTRACT FROM AUTHOR]

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]

Paleoseismic and archaeological records of the Kachchh Rift Basin (KRB) of western India indicates that the region become tectonically active during the period of Middle to Late Holocene. To understand the relationship between strain accumulation, earthquake genesis, and landform development, we analyzed uplifted Late Quaternary terraces and archaeological evidence along the Kachchh Mainland Fault (KMF) zone. Dividing the elevation of the bedrock strath at each site by their ages, yields vertical uplift rates of 0.29–1.17 mm/y for the KMF zones. Archaeological data from the excavation of the Kotada Bhadli site suggest that the site was occupied during the Late mature Harappan (2300-2500 BCE) period and abandoned around 1900 BCE. The ruins of Harappan civilization at Kotada Bhadli location are resting over the Middle Holocene fluvial sediments. The oldest fluvial sediment is dated to 4 ka, whereas the youngest sediment yielded an age of 3 ka. The chronological constraints in geomorphic and archaeological records suggest that the area was hit by an earthquake around 2200 BC (∼3.5ka). The geomorphic and chronologically constrained uplift rates reveal that the KMF zone of the intraplate region of the Kachchh is geodynamically controlled by several fault segments, which are consistent with the ambient tectonic stress field owing to the northward movement of the Indian Plate concerning the Eurasian Plate. [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]

The current geodetic investigation is based on nearly a decade of continuous Global Positioning System (GPS) data towards the western part of the Indian Plate (2009–2019). This research focused on the Kachchh Rift Basin (KRB), the seismically most active intra‐plate region of the Indian Plate, which has seen three ≥ M 7.0 earthquakes in the last two centuries. The GPS stations on the northern and southern margins show SSW and NNE directed motion, indicating that the KRB is currently under the influence of regional compressive stress on both flanks and the same is reflected in the form of earthquake activity in the center portion. Furthermore, the existence of intra‐basin stress, in addition to regional stress, increases strain accumulation and results in the creation of a Principal Deformation Zone (PDZ) in the central part of the KRB. The average annual deformation in the middle of KRB remains 1.0 ± 0.5 mm/year, while sites near the South Wagad Fault (SWF) experience 1.2 mm/year of fault parallel motion. The dominant fault normal motion along the flanks with a maximum fault parallel motion in the middle intimates the existence of strike‐slip tectonics in the central Kachchh. The geometric relationship of strike‐slip faults in a compressive margin and strain accumulation in pre‐existing faults (PDZ) is responsible for current strike‐slip and thrust motion in the Kachchh, including the 2001 Bhuj earthquake (M 7.7). Our geodetic model is well‐corroborated with the geological observations of the wrench fault model of strike‐slip faults. PS‐InSAR results in the northern part of the region between Khadir and Bela Islands show ≤6.0 mm of annual LOS displacement. GPS results indicate ≈ 1.3 to 1.4 ± 0.5 mm/year of fault parallel motion along the transverse Ekal Amrapar Fault (EAF). The non‐significant variation in GRACE‐derived TWS values (from 2009 to 2018) rules out non‐tectonic deformation in the vicinity of EAF and thus points to tectonic activity as the cause of the derived deformation in the region. [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]