ABSTRACT
The Time-Domain Electromagnetic (TDEM) or Transient Electromagnetic (TEM) method, like frequency domain (FEM), is a controlled source EM induction method. It has been widely used in metal ore prospecting and to some extent for deeper explorations over the past several decades. With advancement in instrumentation, portability and data acquisition technology, applications have widened and it is being used for near-surface mapping also. There has been considerable growth in applications of TEM for groundwater exploration where it has been mainly used for sounding depth-wise variations in electrical conductivity within 100 to 200 m depth. These variations can be translated into lithological layers with hydrogeological characteristics, such as unconsolidated and consolidated formations, sand and clay beds, presence of fresh and saline groundwater and conductive contamination plumes etc. It can also be used to assess weathered zone thickness, map resistive bed rock and approximate the presence of conductive shallow fractured zones. Being more responsive to conductive beds like saturated clays and saline water aquifers it has been mostly used in sedimentary terrain for hydrogeological investigations and environmental studies.
