An integrated geostrategy for mapping of structures favourable to ground water occurrence - a case study

Abstract

An integrated geophysical strategy employing magnetic, electrical and refraction seismic methods was used to delineate geological contacts associated with an outlier in biotite gneiss and sandstones located near Tiruvuru, Andhra Pradesh, India. Generally these contacts are favorable for ground water occurrence and exploration. In this study, magnetic method used as a reconnaissance tool was found to be highly effective for delineating contacts and estimating the depths to the basement based on Hilbert transform analysis, Fourier spectral method followed by Geosoft modeling. Also the width of the outlier was established using the amplitude of the analytic signal of the magnetic anomalies. Refraction seismic studies proved to be useful in determining accurately the thickness of various layers. Certain low velocity pockets which are favorable to groundwater accumulation were also identified. Location of contacts was supported by vertical electrical soundings (VES) through pseudo sections; the depth to subsurface contact within the outlier was derived from geoelectrical sections. Reliability of interpretation is substantiated by correlating the signal with known geology and bore well data.