Analysis and Interpretation of In-Phase Component of VLF-EM Data using Hilbert Transform and the Amplitude of Analytical Signal

An interpretation of in-phase anomaly of very low frequency electromagnetic (VLF-EM) data was carried out using the analysis of the Hilbert transform of the in-phase component and the amplitude of its analytic signal. The analysis was used to delineate the source and depth to the top of a subsurface conductive body. The amplitude of the analytical signal of the data was observed to mimic the conventional Fraser-filtered operation and was used to locate the exact location of the anomalous body. The in-phase component with the Hilbert transform yields an approximate depth to the top of the conductor which agree with the result of the vertical electrical sounding conducted at the vicinity of the anomalous body. Keywords: VLF-EM method, Hilbert transform, analytical signal, in-phase, Fraser filtering

Quantitative estimation of natural recharge due to monsoon rainfall using the principle of information theory in the area of Ghorawal block of Sonebhadra district, U.P., India

ABSTRACT The ground water recharge rate due to monsoon rainfall is estimated for the area of Ghorawal block in Sonebhadra district of Uttar Pradesh (U.P.), India, using the entropy method from the principle of information theory. Average water level measured in ten (10) different locations in Ghorawal block and the monsoon rainfall recorded in the district from year 2007 -2010 was used for the analysis. The contribution due to the monsoon rainfall during this period was obtained by calculating the marginal and mutual entropies of the monsoon rainfall and the depth to water level. A ratio of mutual entropy to marginal entropy of rainfall was used as a measure of the fractional amount of rainfall that recharges the ground water resources in the study area. An estimated rate of 12.1% of the rainfall measured during the study period was calculated