July, 2025 || Volume 29 No.04
Volume 29(4) (2025)4-6
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1
Imaging intra-volcanic Mesozoic sediments and shallow crustal configuration from traveltime inversion of long-offset seismic data in Saurashtra basin, India
Renuka Kolluru and Laxmidhar Behera*
CSIR-National Geophysical Research Institute, Hyderabad - 500007, India
https://doi.org/10.71122/JIGU.29(4)2025.0022
ABSTRACT
Saurashtra on-shore basin is considered a major Mesozoic province of India having wide-spread cover of Deccan Traps (basalts), which acts as major impediment for imaging deeper sub-surface geological structures for the exploration of hydrocarbons. The Mesozoic sediments hidden and entrapped within the basalts, as well as other subsurface geological structures, which can be distinctly imaged using the inversion of long-offset seismic traveltime data. Hence, the robust ray-trace inversion technique is employed for the same traveltime data along the 180 km long NW-SE trending Jodia-Ansador seismic profile of Saurashtra basin. This helped to image the sub-surface geological structures and shallow-crustal P-wave velocity model (??) of this region. The ?? model delineated along the seismic profile has five-layers derived from the 2-D ray-trace inversion of both refraction and reflection traveltime data. The low-velocity-layer (LVL) Mesozoic sediments (4.2 km/s) of 0.5-1.0 km thickness is imaged, which is hidden below the high-velocity-layer (HVL) Deccan Traps (4.8-5.2 km/s). Below the low-velocity Mesozoic layer, another HVL (5.4-5.5 km/s) is present, which is considered as Mesozoic volcanics of Jurassic age having thickness variations of 0.5-1.6 km that pinches out towards Ansador. The granitic-gneissic basement (5.8-6.0 km/s) is very undulating having thickness variation of 2.5-3.5 km, forming horst and graben structures along the profile. Below the basement, a relatively high-velocity (6.5 km/s) layer has been delineated, which may be attributed to mid-crustal rocks. It is constrained to a maximum 10 km depth using long-offset seismic reflection data. There is significant up-warping of basement and the mid-crustal layer, which indicate complex geological and tectonic setup because of the Late Cretaceous Deccan volcanism and out-pouring of wide-spread tholeiitic lavas on the surface, masking the hydrocarbon-bearing Mesozoic sediments of the basin.
2
Mapping and demarcating gold mineralization in Jashpur and Raigarh districts (Chhattisgarh) from Analytic Hierarchy Process and geophysical approach
Vishal Bajirao Nayakwdi1 and Dewashish Kumar1,2*
1CSIR-National Geophysical Research Institute, Hyderabad -500007, India
2AcSIR – Academy of Scientific and Innovative Research, Ghaziabad, India
https://doi.org/10.71122/JIGU.29(4)2025.0023
ABSTRACT
Mineral exploration is a vital activity for the sustainable and economic development of any region. This study focuses on the Jashpur and Raigarh districts of Chhattisgarh state in India. We integrate geology, electrical tomography, resistivity, induced polarization (IP) and Geographic Information Systems (GIS) to identify high potential zones of hydrothermal gold deposits. We followed a data driven approach that utilizes multiple data sets pertaining to geological, geochemical and geophysical studies. These data sets in the Analytic Hierarchy Process (AHP) were utilized to provide weights to various evidence layers through expert judgment and literature review. The weighted layers were combined to generate mineral prospective maps, which identified areas with significant economic potential. This study demonstrates the effectiveness of integrating state-of-the-art electrical tomography method and GIS in mineral exploration by providing a robust framework for identifying economically viable gold and other sulphide mineral deposits. Mineral Prospect Map (MPM) indicates that 130.40 sq. km area comes under the class of high mineralized zone. The results contribute to the sustainable development of the Jashpur and Raigarh districts, offering valuable insights for mineral resource management and exploration strategies.
3
Temporal and spatial analysis of dissolved oxygen, sea surface temperature and sea surface salinity in northern Indian Ocean: Implication for environmental trends and variability
Siddharth Srivasatv, Vivek Kumar Pandey*,Yaduvendra Singh and Prabha Kushwaha
K. Banerjee Centre of Atmospheric and Ocean Studies, Institute of Interdisciplinary Studies, Nehru Science Centre, University of Allahabad, Prayagraj - 211002, India
https://doi.org/10.71122/JIGU.29(4)2025.0024
ABSTRACT
The Indian Ocean, a vital part of the world's climate system, influences both local and global environmental trends. Dissolved Oxygen (DO), Sea Surface Temperature (SST) and Sea Surface Salinity (SSS) in the northern Indian Ocean, are three crucial oceanographic parameters that provide a comprehensive temporal and spatial analysis. The main goal is to examine environmental trends and variability in this region, shedding light on the potential impacts of anthropogenic activities and climate change. Using data from the Copernicus Marine Environment Monitoring Service, with resolution of 0.25°, spanning from 1998 to 2020, we aim to understand the physical and biogeochemical dynamics of the Arabian Sea and the Bay of Bengal. The analysis reveals significant temporal and regional patterns in DO, SST, and SSS across the Indian Ocean basin, including clear seasonal variations, temporal long-term trends, and notable annual cycles. Variations in DO concentrations underscore the vulnerability of marine life to hypoxic or anoxic conditions, which could negatively affect biodiversity. Our results and statistical analyses emphasize the critical importance of ongoing monitoring and research in the northern Indian Ocean to understand the environmental changes occurring in this region. This study provides valuable insight into the intricate interplay of environmental trends and variability through a detailed examination of the temporal and spatial dynamics of DO, SST and SSS in the Northern Indian Ocean. It highlights the urgent needs for proactive measures to mitigate the impacts of climate change and human activities on this essential marine environment.
4
Seismic risk assessment using analytic hierarchy process: An integrated approach for Varanasi city, India
Shashank Shekhar1, Anurag Tiwari1, 2*, J. L. Gautam2 and G. P. Singh1
1Department of Geophysics, Banaras Hindu University, Varanasi-221005, India
2National Centre for Seismology, Ministry of Earth Sciences, New Delhi-110003, India
https://doi.org/10.71122/JIGU.29(4)2025.0025
ABSTRACT
Seismic hazards present significant risks to urban areas, highlighting the need for a comprehensive earthquake risk assessment (ERA) to enhance disaster preparedness. This study utilizes the Analytic Hierarchy Process (AHP) methodology to construct an integrated ERA map using Geographic Information System (GIS) for Varanasi city, which is one of the most densely populated cities of Northern India, located in the Indo-Gangetic plain. The AHP framework created a pairwise comparison matrix to assess the relative significance of factors affecting seismic risk, such as peak ground acceleration, geology, geomorphology, building density, population density, literacy, transports and building typology. Weights were based on global studies with similar characteristics, expert advice and consistency checks to ensure coherence in comparisons. Integrated AHP model is used to generate seismic hazard index and vulnerability index which is then integrated to develop a comprehensive seismic risk map using GIS. As a result, Varanasi City is classified into five zones of seismic risk levels, ranging from very low to very high for the seismicity occurrence with a 10% probability of exceedance and a 2% probability of exceedance in 50 years. Our study finds that 6.92% of the area of Varanasi city lies in the very high seismic risk zone (Zone 5), followed by 23.88% in high risk, 21.32% moderate, 20.25% low, and 27.66% very low risk (zone 1) for the seismicity occurrence with 10% probability of exceedance in 50 years (DBE). For a 2% probability of exceedance in 50 years (MCE), the distribution slightly changes, with 26.14% in very low, 21.24% low, 23.31% moderate, 21.69% high, and 7.62% area lie in very high seismic risk zones (Zone 5).
5
Investigation of particulate matter in Perungudi, Chennai, Tamil Nadu (India) during the winter period
S. Tamil Selvi*1 and S. Najma Nikkath2
1 Department of Physics, KCG College of Technology, Chennai-600 097, Tamil Nadu, India
2 Department of Physics, Bhaktavasalam Memorial College for Women, Chennai-600 080, Tamil Nadu, India
https://doi.org/10.71122/JIGU.29(4)2025.0026
ABSTRACT
Air pollution studies have found that the coarse and fine particulate matter are mainly responsible for various respiratory health effects for humans. This study focuses on the distribution and changes in the concentrations of PM10 and its precursors (SO2, NO2 and CO) in Perungudi, Chennai. Perungudi is chosen as the study area, as it is located on both commercial and residential site. The acquired data is used to estimate the various concentration levels of particulate pollution during the winter season of January and February 2022, using Pearson correlation and linear regression models .This statistical study helps in identify the significant relationship between the various pollutants SO2, NO2 and CO with PM10. Pearson correlation and linear regression models were applied to evaluate the dependence of PM10 concentration on its precursors based on daily values. The correlation results indicated positive low and moderate values. The regression R2 values show the variation of 20% to 25%. This study is an effective step toward a better understanding of PM10 changes in Perungudi under the changing influence of precursors.
6
Possible extension of Proterozoic sediments beneath Eastern Ghats Belt: A case study of Bastar Craton
Ankita Roy1, Swarnapriya Chowdari2 and A. Vasanthi 2*
1Department of Earth Sciences, Pondicherry University, Puducherry-605014, India
2CSIR-National Geophysical Research Institute, Hyderabad-500007, India
https://doi.org/10.71122/JIGU.29(4)2025.0027
ABSTRACT
The eastern margin of the Indian shield presents a geologically and geotectonically intricate zone where Proterozoic sedimentary basins and the high-grade metamorphic Eastern Ghats Belt (EGB), are juxtaposed along a broad, shear-dominated contact stretching from Odisha in the north to northern Tamil Nadu in the south. The tectonic relationship between the Bastar craton and the Eastern Ghats Belt in eastern India, has been the subject of considerable geological interest due to its implications for Proterozoic crustal evolution, basin development, and the assembly of ancient continental blocks. In this study, satellitederived gravity data over Bastar craton and adjoining regions have been analysed to explore the possible extension of Proterozoic sedimentary sequences of this craton beneath EGB. The presence of a prominent residual gravity low of the order of -50 mGal on the SE part of the study area has been delineated below the EGB terrain, indicating possible presence of Mesoproterozoic to early Neoproterozoic sedimentary sequences. Further, gravity modelling across the Bastar craton and EGB, reveals steep crustal-scale contacts and high-density zones that are consistent with a under-thrust geometry. The underthrusting of Bastar sediments beneath the EGB likely occurred during the Mesoproterozoic collisional events, linked to the Rodinia supercontinent assembly. These findings not only enhance our understanding of the tectono-thermal history of the Bastar craton and EGB interface, but also provide a framework for reevaluating crustal accretion processes along the cratonic margins in the Indian shield.