The Kachchh rift basin (KRB), located in the western continental margin of India, is very important due to repeated large magnitude occurrence of intraplate earthquakes. The present study elucidates ...the subsurface structural features using wavelength filtering, total horizontal derivative (THD) and 2.5 dimensional (2.5D) density modelling of the gravity data. Power spectrum analysis of the gravity data gives the cut-off wavelength of 100 km that has been used for wavelength filtering for regional-residual separation. The residual gravity anomaly significantly enhances the shallow features (like Allah-Bund fault, Kachchh mainland uplift, Wagad uplift, and Pachham uplift) and gives an NW–SE subsurface structural trend. The predominant direction for major lineaments derived by the THD of gravity data shows the ENE–WSW as well as NE–SW and NW–SE directions. The 2.5D density model of the regional gravity anomaly reveals the presence of high-density magmatic underplating layer and intrusive mafic body in the lower crust that is in accordance with the previous studies. The regional slope of the Moho in the KRB is towards the SW direction. An intrusive mafic body in the lower crust and volcanic plugs in the upper crust act as stress concentrator which is responsible for seismicity in the KRB. Several new lineaments have been identified based on the present study, which may be accountable for seismicity over the different part of KRB.
India, with 80 % energy demand reliant on fossil fuels, is the world's third-largest greenhouse gas emitter, necessitating a shift from fossil fuels to renewable energy. While solar and wind ...production has grown, geothermal energy remains untapped despite enormous prospects in the country. In this regard, India's first regional-scale geothermal potential (GP) map has been prepared using a GIS based on a multi-criteria decision analysis technique. Five thematic layers (geology, fault, heat flow, thermal spring, and earthquake epicenter) have been used to calculate GP index, which is divided into high, moderate, and low categories. The result shows that most geothermal drilling sites are distributed in the high GP category zone, showing high efficacy. Further, a joint study of the geothermal surface and reservoir temperature with the present study shows that the northern and western parts of India have significant potential for geothermal exploration. Our result also reveals that the projected CO2 emissions are approximately 2.6 gigatons (which is lower than other energy sources) for an output of 10 GW using geothermal energy in the next 75 years. This study can enhance geothermal prospect identification, cutting exploration costs, and site selection, and contributing to multiple UN Sustainable Development Goals.
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The Cambay rift (CR) is a rich petroleum province of north-western India and extensively studied for petroleum exploration and mapping the sub-surface structure through various geophysical studies. ...However, the CR is not studied so far towards mapping the geological structures, like faults/lineaments and estimating their source depths. In the present study, the lineaments in the CR have been delineated and their source depths are estimated using satellite-derived EIGEN-6C4 gravity data, though different modern processing techniques (Total Horizontal Derivative (THD), Analytical Signal (AS), Tilt Derivative (TDR) and Euler deconvolution). The majority of the identified lineaments are trending in NW-SE and NE-SW direction and their source depths range between 4.4 and 15 km, indicative of shallow subsurface features in this area. This study provides an updated tectonic map, which offers a better understanding of the structural framework and tectonic setting of the area.
The Cambay rift basin (CRB) is an intracratonic rift in the western part of India. The basin assumes great importance in petroleum exploration owing to the presence of thick hydrocarbon bearing ...sedimentary rocks. Previous investigations using deep seismic soundings (DSS), gravity and heat flow data reveal that the CRB is characterised by a thin crust, high heat flow and high density lower crust. In this study, a detailed crustal structure of the basin is presented by performing a 2.5D density modelling of the EIGEN-6C4 gravity data. Present study attempt to find a plausible explanation for the variation in the Bouguer anomaly (BA) values from +20 to −50 mGal within the basin. It refined the crustal model that is constrained using results from radial average power spectrum (RAPS) analysis of gravity data along with previous seismological and geophysical studies, which reveals that the values of average sedimentary and Deccan Traps thickness are in the order of 4–5 and 1.5–3 km, respectively, along the rift. It also presents possible evidences for a high density underplated layer of thickness 7–15 km along the central part of the CRB. To study the deep-seated features, upward continuation of the BA is carried out at heights of 30, 40 and 50 km. The extension of underplating layer is noticed in the present crustal model and in the upward continued BA in the western part, while it merges with the Moho in eastern part of the CRB. The Moho depths, varying from 31 to 37 km, are found to be shallower inside the CRB than the surroundings. It is inferred that the high BA values in the basin are due to the combined effect of the high density underplated layer in the lower crust and a shallow Moho.
A gravity survey was carried out to estimate the sedimentary thickness and to map upper crustal geometry over the northern part of the Cambay rift. Structural lineaments delineated using the total ...horizontal gradient of the Bouguer anomaly indicate a major lineament trend in the NW-SE direction. Results of the density modelling using residual Bouguer anomaly reveal the average thickness of the Quaternary and Tertiary sediments to be between 0.5 and 6 km, while the Deccan trap thickness varies between 0.5 and 3 km. It is seen that the Mesozoic sediment (maximum thickness ∼0.6 km) is sandwiched between the Deccan trap and granitic basement, which indicates the possible existence of a rift in the late Jurassic-early Cretaceous. Based on the residual Bouguer and density modelling results, the spatial locations of the NE-SW trending Unhawa ridge and the N-S trending Mehsana uplift are provided, which are believed to be the remnant rock of the Proterozoic age. A high-density body, interpreted as a magmatic underplating layer, is also found in the lower part of the middle crust along the central part of the rift, which continues in the lower crust. The magmatic underplating layer is formed during the Reunion hotspot and lithospheric interaction in the Cretaceous period.
In the face of the global groundwater crisis and climate change challenges, the groundwater potential (GWP) and quality (GWQ) assessment for tackling the depletion and contamination of aquifers are ...imperative for India's sustainable development of groundwater resources. This study explores the GWP and GWQ in the southwestern part of Bihar state, located in the declining groundwater of the lower Indo-Gangetic plain, where population growth, rapid urbanization, and escalating agricultural demands have strained aquifer systems. This study uses the Analytical Hierarchy Process and weighted average techniques in the GIS framework to assess groundwater vulnerability. Our results reveal that over 82% of the area exhibits good groundwater potential, except for the southern part. The presence of Vindhyan mountains in the southern part has different geology, elevation, and land use and land cover, leading to poor groundwater potential. Considering the desirable and acceptable limits by BIS (2012) and Who (2022), it has been found that 89% and 18% of the study area falls under the poor to unsuitable groundwater category, affecting a staggering 7.7 million and 1.6 million individuals, respectively despite substantial groundwater potential. Findings from this investigation indicate that groundwater contamination resulted from anthropogenic and geogenic factors; however, it remains suitable for agricultural purposes. Our research will assist policymakers in implementing sustainable management strategies to ensure a lasting and reliable supply for domestic and agricultural uses of groundwater.
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•Southwestern Bihar has good groundwater potential, except in Vindhyan mountains.•89% of study area falls in poor groundwater quality (GWQ) within desirable limit.•7.7 million population is affected by poor GWQ within desirable limit.•18% of study area lies in unsuitable GWQ within acceptable limit.•1.6 million people have been affected by unsuitable GWQ under acceptable limit.
The 1819 Allah-Bund earthquake (ABE) that occurred in the north-western part of the Kachchh rift, India, was a deadliest intraplate earthquake of the nineteenth century. In this work, we have used ...WGM 2012 global gravity model data to understand the tectonic framework in the epicentral zone of the 1819 ABE and surrounding regions. Total horizontal gradient analysis of the Bouguer anomaly (BA) is carried out to map major lineaments in the study area. The logarithmic amplitude spectra of the BA provide the average depth of 13 km between the interface of the upper crust and the basement while basement-sediment interface is found at 1.6 km. The low-pass filter anomaly of cut-off wavelength of 100 km is considered as the regional anomaly. The residual anomaly shows high value with a NW–SE trend which is similar to the trace of Allah-Bund (AB) on the surface. The upper crustal geometry of the region is provided for the first time by performing 2.5D forward gravity modelling along two profiles. These are constrained by seismological and well data. Our present model reveals that the upper crustal thickness increases towards the AB. Inversion of the BA reveals the NW dipping Moho in the study area. The basement is undulating, which is uplifted by 1–2 km over the AB. We also tried to explain the seismicity in the study area. The present study provided the first geophysical evidence of the ABF, and it is inferred that the fault is shallow in nature, dipping in the SW direction.
The Ambaji–Deri region is located in the northeastern part of the Gujarat state of India and is well-known for hosting lead–zinc–copper minerals deposits. Recently, gravity and magnetic data are ...collected in the region with the objective of geological and structural mapping of the area. This data is further processed using upward continuation, derivative analysis, and 2.5-dimensional gravity modelling to understand the subsurface geometry for mineral exploration. The upward continued regional gravity anomaly reveals high value in SW part of the region. The residual gravity and magnetic anomaly show the NE–SW trend, which is sympathetic with the general trend of Delhi supergroup. The high values of the residual Bouguer and the magnetic anomaly at the junction of the Jaisalmer–Barwani and the Chambal–Jamnagar lineaments are inferred as possible potential sites for sulphide mineralisation. The horizontal gradient of the tilt derivative (HGTD) of both the gravity and the magnetic anomalies reveals NE–SW trending lineaments. Based on the results of HGTD, several new structural features have been identified and a refined lineament map of the study area is proposed. The gravity modelling using residual Bouguer anomaly could delineate a high-density intrusive body in the upper crustal level. The result of the gravity model also confirms that the middle crust is uplifted by 1–3 km in the eastern part of the study area. In this study, three prospective zones for base metal mineralisation have been identified.
The Kachchh Mainland Fault (KMF) in the central position of the Kachchh paleo rift basin of the northwestern India is the main fault system where the reverse movement started along preexisting normal ...fault planes during postrift tectonic inversion at end of the Tertiary period. We present the analyses of transient electromagnetic data at 68 sites, distributed along nine traverses across the KMF zone within the Kachchh Mainland. The resistivity sections across the KMF zone do not only image the shallow subsurface geometry of the fault but also delineated synthetic and antithetic splays of the primary faults. An experimentally estimated scaling factor from the late‐time TEM response, which is a proxy for fracture density of the geological formation, is well coincides with the fault zones that are delineated in the present study. The subsurface resistivity structure infers in general north‐dipping reverse faulting along the various segments of the KMF. Some of the en echelon splays form flower structure scenario, suggesting either presence of localized preserved transtensional features in this regional compressive regime or a combination of both positive and negative flower structure scenarios. The observed anomalous deep conducive zones in the fault zone could qualitatively suggest neotectonic activity in the region. The study supports the presence of oblique to transverse faults that bisects the primary KMF. We opined that these transverse structures along with the splays could play a key role in transferring part of stress that being accumulating in the KMF zone.
Key Points
The study gives high‐resolution shallow subsurface image of the Kachchh Mainland Fault, its splays in the active intraplate region
The study provides geophyscical evidence of neotectonic activity in the Kachchh intraplate region
The study provides geophysical evidence of localized preserved transtentional geometry in the regional compressive region
Lithospheric rheological heterogeneities across a rift play a significant role in intraplate deformation and seismic activity. The Kachchh rift in the northwestern part of the India has not only ...experienced lithospheric stretching but also witnessed large magnitude devastating earthquakes. Here, we present the results of a magnetotelluric (MT) investigation carried out in the southeastern part of the Kachchh intraplate region illuminating the seismogenic zone of the 1956 Anjar earthquake (Mw 6.0). The two-dimensional geoelectrical model derived from the MT data acquired at 21 sites along a NE-SW profile reveals assemblage of conductive and resistive zones in the upper and the mid crustal depths in the close vicinity of the major fault zones and the hypocentral depths. The results reveal a very high conductive zone near the Moho, affirming the presence of an upper mantle fluidized zone. Unlike the South Wagad Fault, the Kachchh Mainland Fault and the Katrol Hill Fault do not have a downward lower crustal extension, and terminate at the mid crustal depths. We suggest that the presence of trapped fluids in the brittle-ductile transition zone (12–15 km) and their seepage to the resistive plutons might be a possible mechanism for triggering the 1956 event as well as the current seismic activity in the region.
•Evidence for trapped fluids in the seismically active Kachchh intraplate region.•High level of upper crustal heterogeneity beneath the epicentral region of the Anjar earthquake.•A plausible model for genesis of large magnitude earthquakes in the Kachchh region.
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