Deep subsurface measurements in Herve and Dalhem

The University of Liège and RWTH Aachen University will soon be conducting so-called “deep” ERT measurements in the outskirts of Herve and Dalhem. These measurements are part of the campaigns to map the deeper subsurface in the search area for the Einstein Telescope.

The measurements are scheduled to take place from 30 June to 4 July. Preparations will begin a week earlier. No special measures are required for these measurements and residents living along the route or through traffic will not be inconvenienced. Agreements have been made with the municipalities of Herve and Dalhem and with private landowners regarding the measurements. The client for the measurements is the Einstein Telescope EMR project office, which is responsible for the feasibility studies for the construction of the underground telescope in the Euregio Meuse-Rhine.

ERT measurement

In these so-called “deep electrical resistivity tomography” or ERT measurements, a cable with a diameter of 2 millimetres is laid along the side of public roads and paths or on private land over a length of more than 5 kilometres. These measurements mainly concern the roads Larbuisson, Fosselette and near the Mortroux forest.

Electricity is injected into the ground via this cable at two locations. In order to measure the voltage in the ground, a total of 35 measuring stations are placed along the route every 150 metres. These stations consist of the measuring device itself and three electrodes connected by cables for each station. The measurement of the electrical resistance via these 35 points provides a picture of the deeper subsoil.

Noise measurement

On a small section of the route, approximately 500 metres long, the researchers are combining the ERT measurements with noise measurements. For this purpose, 48 geophones are being used. These sensors do not emit any light or sound signals.