ABEM - TEM Solutions
The transient electromagnetic (TEM or time domain electromagnetic TDEM) method is extremely effective in determining electrical conductivity of the subsurface at depths from a few meters down to several hundred meters. Since electrical conductivity of soil correlates strongly with soil properties, TEM is a powerful tool for mapping of conductive layers and is commonly used for mapping sand and gravel aquifers, clay layers restricting groundwater flow, conductive leachate in groundwater, saltwater intrusion, and depth to bedrock.
The TEM method has been used for mining exploration for several decades but more recently has undergone a renaissance. Improved electronics and signal processing now allow for acquisition of high quality data for the interpretation and determination of a sedimentary geology.
ABEM, in partnership with Aarhus University, has made a significant contribution to the advancement of the TEM technology resulting in solutions capable of accurately resolving subtle changes in geology in fine detail with excellent penetration of depth.
Complementary to DC Resistivity
The TEM method has several advantages over the versatile and robust DC resistivity method. TEM does not require large electrode arrays, and therefore is less sensitive to lateral changes in the soils.
DC resistivity requires long electrode spreads with lengths that are typically three to five times the depth of exploration. TEM techniques can obtain depths of exploration of a few hundred meters using a 40 x 40 meter transmitter loop.
TEM often has better depth resolution than DC resistivity, particularly for mapping conductive (confining layers) in resistive sections. The TEM technique can efficiently map conductive strata (e.g. aquitards) below a resistive layer.
TEM should preferably be deployed outside urban areas.