Identifications of fractured zones in part of hard rock area of Sonebhadra District, U.P., India using integrated surfac
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ORIGINAL PAPER
Identifications of fractured zones in part of hard rock area of Sonebhadra District, U.P., India using integrated surface geophysical method for groundwater exploration Lazarus G. Ndatuwong & G. S. Yadav
Received: 17 November 2012 / Accepted: 3 February 2013 # Saudi Society for Geosciences 2013
Abstract Surface geophysical methods were used to determine the locations of fracture zones in part of the hard rock area in Sonebhadra District of Uttar Pradesh, India. The survey comprises three DC resistivity profile using the gradient profiling technique and ten very low frequency electromagnetic (VLF-EM) traverses profiles. The methods were used over survey lines extending between 200 and 400 m; the results were correlated to locate fracture zones for the purpose of groundwater exploration. Qualitative interpretation of the VLF-EM was carried out using Fraser and Karous–Hjelt filters. The result of the interpretation revealed a number of subsurface zones with high real component current density that defines the potential subsurface features (probably fracture zones). The subsurface feature concurred with the low resistive zones indentified from the gradient resistivity profiling. The zones where further inferred quantitatively using data obtained from DC resistivity sounding at some selected anomalous points. The result obtained proves the efficiency of integrating both methods in detecting fractures zones in hard rock area.
Introduction
Keywords Fractures . Hard rock . Groundwater . VLF electromagnetic . Gradient profiling . Resistivity
Geophysical survey
L. G. Ndatuwong (*) : G. S. Yadav Department of Geophysics, Banaras Hindu University, 221005 Varanasi, India e-mail: [email protected] L. G. Ndatuwong Department of Physics, Adamawa State University, PMB 25, Mubi, Adamawa State, Nigeria
The location and orientation of fracture zones is an important aspect of groundwater exploration and also for modelling fluid flow and contaminant transport in hard rock areas. Surface geophysical methods are a rapid, inexpensive addition to drilling for determining the locations and orientation of fractured zones in hard rock area (Powers et al. 1999). The role of geophysical methods in groundwater exploration is vital. Depending upon the scale of operation, geophysical surveys help to delineate regional hydrological features or pinpoint locations for drilling boreholes. It also has an advantage of providing spatial extensive information about subsurface in a minimal invasive manner and comparatively high resolution than the conventional methods. Geophysical survey can be used solely or together with supporting data from hydrogeology and borehole to optimise well sitting and fracture detection (Hubbard 2011).
Gradient profiling survey Gradient profiling is generally used to locate lateral inhomogeneity or vertical contacts. This is achieved by moving a fixed electrode configuration from point to point along a profile. The convectional Wenner and Schlumberger arrays has found great application in profiling wor
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