Determination of Underground Structure and Migration of Hot Plumes Contaminating Fresh Water Using Vertical Electrical Survey (VES) and Magnetic Survey, A Case Study of Tattapani Thermal Spring, Azad Kashmir

Abstract

A geophysical survey was carried out at Tattapani thermal spring Azad Kashmir to delineate structure, thickness, depth, lithology and migration of hot plumes contaminating fresh water. The study area was investigated by Vertical Electrical Sounding (VES) using schlumberger array at 21 locations arranged in ten profiles to a maximum depth of 500 m and 200 magnetic observations. The extension and tectonic setup of thermal spring was mapped by geoelectrical litho sections, subsurface geological sections (20m, 20-100m and 100-500m) pseudo section, apparent resistivity map, geoelectrical parameters, statistical distribution of apparent resistivity, total magnetic intensity and anomaly map. The data show that Tattapani hot spring is concentrated along the fault line delineated by geoelectrical litho sections and magnetic section with value of -120 nT to -300 nT, total field intensity of 50000-50450 nT and confirm by macro anisotropy (1.0 to 2.7). The geoelectrical lithological section portrays that study area comprises lithological fabric of dolomite (≥400 ohm.m), sandstone (150-200 ohm.m), clay (80-150 ohm.m), Shaley clay (50-80) and shale (≤ 50). The Thermal Plumes (10-70 ohm.m) were pictured by resistivity section and pseudo section at average depth of 30-60 m and showing migration of hot plumes in the North-Eastern direction contaminating fresh water (100-200 ohm.m). The longitudinal conductance (0.95-15 mhos), transverse resistance (20-300 ohm.m²) are seen having maximum value in the North-Eastern and North-Western side of the study area. The study also shows that fresh ground water is mostly concentrated in sandstone (150-200 ohm.m), dolomite (≥400 ohm.m) and lies above the thermal plumes and thus highly prone to contamination due to upwelling of thermal water.