A large-scale international experiment is set to examine the deep underground in the Vogtland region and northwestern Bohemia. The German-Czech border region around the Eger Basin has been experiencing frequent earthquake swarms for centuries. Now, the GFZ Helmholtz Centre for GeoResearch, together with universities in Potsdam, Leipzig, Freiberg, Jena, Munich, Erlangen, and Münster, as well as the Geological Service in Saxony and the Academy of Sciences in Prague, is setting up almost 300 temporary seismic stations over an area of 100 by 100 kilometres.
"We expect that the many stations will enable us to detect and investigate the smallest earthquake swarms that would otherwise remain hidden. In addition, we will then have the opportunity for the first time to search for low-frequency deep earthquakes across a wide area, such as those recently discovered in the volcanic regions of the Eifel and the Massif Central in France. This could answer the question of whether magmatic melts are still rising to a depth of ten kilometers beneath the Vogtland region today,“ says Dr. Pinar Büyükakpinar from the GFZ. She is the scientific coordinator of the experiment and lead author of the study on the most recent earthquake swarm there, the ”Klingenthal swarm" of 2024.
Background
Earthquake swarms have been occurring for centuries in the German-Czech border region around the Eger Basin (Vogtland and northwestern Bohemia). This unusual phenomenon is far away from tectonic plate boundaries and active volcanic systems. Over a period of several weeks and months, thousands of small micro earthquakes occur with high intensity but without a strong main quake to follow.
In 2024, the last major swarm occurred near the town of Klingenthal, activating a zone that was already active 125 years ago and introduced the term “earthquake swarm” into science at that time. In the Eger Basis, natural carbon dioxide (CO₂) also rises to the surface at mineral springs and so-called mofettes. The CO₂ originates from the upper mantle at a depth of more than 30 km. The Vogtland region and northwestern Bohemia are also known for their many thermal springs and spas.
The cause of all these phenomena is still not fully understood. Scientists assume that all observations are an expression of magmatic processes in the lower crust and upper mantle of the Earth.
The GFZ will provide nearly 300 seismic stations from its Geophysical Instrument Pool (GIPP). Dr. Marius Isken, technical coordinator of the large-scale experiment, says: “Our highly sensitive sensors will record ground vibrations over an area of 100 by 100 kilometers over a period of 12 to 18 months. These vibrations are triggered by earthquake swarms and CO₂ emissions, but also by weather and traffic.”
Scientists hope that this unique Large N experiment will provide a more accurate picture of the Earth's crust. The term “Large N” refers to the large number (N) of sensors. In particular, the complex structure of the Earth's crust will be mapped using tomography. “Here, three different continental plates have interlocked, overlapped, and formed larger granite complexes in the geological past,” says Professor Torsten Dahm, project manager at the GFZ.
Further contact persons:
- Saxony State Office for the Environment, Agriculture and Geology: Dr. Lutz Sonnabend, Lutz.Sonnabend@lfulg.sachsen.de , Lutz.Sonnabend@smekul.sachsen.de
- Earthquake Service Bavaria / LMU Munich: Dr. Joachim Wassermann, j.wassermann@lmu.de
- FSU Jena: Prof. Dr. Ulrich Wegler, ulrich.wegler@uni-jena.de
- IG CAS, Prague, Czech Republic: Dr. Jana Doubravova, doubravka@ig.cas.cz
You can access the electronic project mailbox at: elise-info@gfz.de