Einstein Telescope Site Study: 650 Geophones Listen to the Subsurface

25 June 2026

Photo: Dirk Becker

3-Component geophone installation close to wind turbines

To prepare for the Einstein Telescope, a large-scale geophone array now listens to the subsurface in the so-called Euregio Meuse-Rhine (EMR) region, helping evaluate its suitability for hosting a future gravitational wave detector. Working alongside colleagues from Belgium, the Netherlands, and RWTH Aachen University — and under the leadership of the University of Liège — approximately 650 sensors were installed across 30 municipalities in the region spanning Aachen, Maastricht, and Liège. These devices record ground motion at the surface, which in this area is significantly influenced by human activities such as trains, wind turbines, and industrial facilities. The aim of these studies is to gain a better understanding of the sources of seismic background noise and to investigate their impact on the region's wave field. This is of particular interest because the region is a potential future site for a next-generation gravitational-wave telescope: the Einstein Telescope.

The Einstein Telescope is designed to measure minute ripples in spacetime. These so-called gravitational waves cause infinitesimal changes in length at the telescope's location, which can be measured using lasers. The sources of these gravitational waves are the mergers of extremely massive celestial bodies, such as black holes or neutron stars. Studying such phenomena provides a better understanding of the evolution of the early universe, the formation of black holes, and the completeness of current laws of physics. Since the instruments required for these measurements are extremely sensitive, any potential sources of interference — such as ground motion — must be minimized or, at the very least, precisely characterized so that their impact on the measurements can subsequently be calculated and corrected. 

To ensure high-quality recording of ground motion, the geophones must move in unison with the surrounding subsurface. To achieve this coupling between the sensors and the ground, small holes were dug for their installation. Additionally, the devices capable of recording all three components of the wavefield were leveled and aligned to the north. Precise geophone locations were determined using GPS to facilitate later retrieval. These fully autonomous units record data over a period of approximately four weeks. As part of the campaign, the University of Hamburg team participated in the installation of around 100 sensors, deploying stations at a wide variety of sites across the Netherlands, Belgium, and Germany.