tTEM: experiences in the Netherlands of this novel Electro Magnetic data acquisition technique

A novel way of collecting electromagnetic measurements makes use of an All Terrain Vehicle (ATV) that pulls a transmitter and receiver. This so-called towed Transient Electro Magnetics system (tTEM, described in detail by Auken et al, 2019)  provide a fast way to obtain 3-dimensional images of the electrical resistivity of the subsurface. The unprecedented and speedy spatial coverage that can be obtained by the technique is a clear advantage over other land-based EM techniques. The technique acquires data with a speed of 10-15km/h, resulting in large coverages per day in open terrain (meadows, agricultural fields). The depth of investigation varies from 60 – 100m, depending on the characteristics of the subsurface (resistive or conductive). We present results here that are taken from various projects in the Netherlands, ranging from mapping buried glacial valleys, continuity of clay layers for groundwater protection, trying to detect faults and to investigate the lateral extent of Holocene clay deposits for dike reinforcements studies. We find the application of the tTEM technique for characterizing typical Dutch subsurface very useful, providing excellent insight in the 3D distribution of clay layers.

Auken, Esben, Nikolaj Foged, Jakob Juul Larsen, Knud Valdemar Trøllund Lassen, Pradip Kumar Maurya, Søren Møller Dath, and Tore Tolstrup Eiskjær, (2019), "tTEM — A towed transient electromagnetic system for detailed 3D imaging of the top 70 m oaf the subsurface," GEOPHYSICS 84: E13-E22. https://doi.org/10.1190/geo2018-0355.1.