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Transient EM – TEM

Transient EM (TEM) is an electromagnetic method, where a constant current is fed into the cable. When the current in the loop is abruptly turned off, an electromagnetic field will be generated that in turn will induce electrical currents in the ground immediately below the cable loop. The current is migrating downwards and outwards from the transmitter loop. The velocity of this migration is dependent on the resistivity of the ground. The current in the ground is causing a secondary magnetic field which is measured by mean of a receiver coil. Sampling is carried out at different time intervals (time windows or channels) after current shut-off in order to get information on the resistivity variations with depth. Results are presented as a 1D section of the resistivity distribution as a function of depth.

GeoVista possess a TEM-system (TerraTEM) with a 3-components receiver. We also possess a probe (VECTEM V) that enables surveying in boreholes as deep as 1400 meters.

Reference projects:

– Various TEM surveys for exploration purposes.