• S Thiagarajan

      Articles written in Journal of Earth System Science

    • Seismically constrained two-dimensional crustal thermal structure of the cambay basin

      S Thiagarajan D V Ramana S N Rai

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      The temperature field within the crust is closely related to tectonic history as well as many other geological processes inside the earth. Therefore, knowledge of the crustal thermal structure of a region is of great importance for its tectonophysical studies. This work deals with the two-dimensional thermal modelling to delineate the crustal thermal structure along a 230 km long Deep Seismic Sounding (DSS) profile in the north Cambay basin. In this work P-wave velocities obtained from the DSS studies have been converted into heat generation values for the computation of temperature distribution. The model result reveals the Curie isotherm at a depth of ≈22 km and Moho temperature at around 900‡C.

    • 2-D Crustal thermal structure along Thuadara–Sindad DSS profile across Narmada– Son lineament, central India

      S N Rai S Thiagarajan

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      Central India is traversed by a WSW–ENE trending Narmada–Son lineament (NSL) which is characterized by the presence of numerous hot springs, feeder dykes for Deccan Traps and seismicity all along its length. It is divided in two parts by the Barwani–Sukta Fault (BSF). To the west of this fault a graben exists, whereas to the east the basement is uplifted between Narmada North Fault (NNF) and Narmada South Fault (NSF). The present work deals with the 2-D thermal modeling to delineate the crustal thermal structure of the western part of NSL region along the Thuadara–Sindad Deep Seismic Sounding (DSS) profile which runs almost in the N–S direction across the NSL. Numerical results of the model reveal that the conductive surface heat flow value in the region under consideration varies between 45 and 47mW/m2. Out of which 23mW/m2 is the contribution from the mantle heat flow and the remaining from within the crust. The Curie depth is found to vary between 46 and 47 km and is in close agreement with the earlier reported Curie depth estimated from the analysis of MAGSAT data. The Moho temperature varies between 470 and 500°C. This study suggests that this western part of central Indian region is characterized by low mantle heat flow which in turn makes the lower crust brittle and amenable to the occurrence of deep focused earthquakes such as Satpura (1938) earthquake.

    • Finite element modelling of elastic intraplate stresses due to heterogeneities in crustal density and mechanical properties for the Jabalpur earthquake region, central India

      A Manglik S Thiagarajan A V Mikhailova Yu Rebetsky

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      Deep lower crustal intraplate earthquakes are infrequent and the mechanism of their occurrence is not well understood. The Narmada–Son-lineament region in central India has experienced two such events, the 1938 Satpura earthquake and the 1997 Jabalpur earthquake, having a focal depth of more than 35 km. We have estimated elastic stresses due to the crustal density and mechanical properties heterogeneities along the Hirapur–Mandla profile passing through the Jabalpur earthquake region to analyse conditions suitable for the concentration of shear stresses in the hypocentral region of this earthquake. Elastic stresses have been computed by a finite element method for a range of material parameters. The results indicate that the shear stresses generated by the density heterogeneities alone are not able to locally enhance the stress concentration in the hypocentral region. The role of mechanical properties of various crustal layers is important in achieving this localization of stresses. Among a range of material parameters analysed, the model with a mechanically strong lower crust overlying a relatively weak sub-Moho layer is able to enhance the stress concentration in the hypocentral region, implying a weaker mantle in comparison to the lower crust for this region of central India.

    • Delineation of aquifers in basaltic hard rock terrain using vertical electrical soundings data

      S N Rai S Thiagarajan Y Ratna Kumari V Anand Rao A Manglik

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      The region under investigation for groundwater exploration is a part of the eastern fringe of Deccan traps in Kalmeshwar Taluk of Nagpur district. In this region, groundwater is the main source of water supply for drinking and irrigation purposes. Presently, the known source of groundwater is the upper weathered mantle in the depth range of 8–15 m. This source of groundwater has been overexploited because of increasing demand of water supply and is unable to meet the present requirement. The present work deals with the delineation of new sources of groundwater at deeper levels concealed within and below the traps by using vertical electrical sounding surveys in order to meet the increasing demand of water supply.

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