Test measurement in the GFZ underground laboratory

As part of the HIL project, an additional test measurement was conducted at the Underground Laboratory in Freiberg. The objective was to test various seismic sources in combination with different types of receivers under real conditions. Particular attention was given to the first successful test of the newly developed borehole double source, which is designed for use in boreholes with a diameter of 96 mm. 

Prior to the start of measurements, the condition of two boreholes, 70 m and 50 m in length respectively, was inspected. One of the boreholes was clogged with sediment and had to be flushed before the sensors could be safely installed. To document and assess the condition of the boreholes, camera inspections were carried out in both, providing supplementary visual information on the internal structure. A newly developed camera system was used for this purpose, which stood out particularly due to its high resolution and natural colour rendering.

The receivers were installed in a second borehole as well as along the underground drift. This arrangement enabled a differentiated recording of seismic signals from various spatial directions and distances. Different types of sensors were used—including Wilcoxon sensors, piezoelectric sensors, and conventional geophones. The comparative measurements serve to evaluate and further develop the sensor technology for future underground applications.

The results of the campaign make an important contribution to the advancement of geophysical measurement techniques. Once again, the Underground Laboratory in Freiberg demonstrates its role as an innovative site for research and testing.