Project Elise

Large-scale seismic experiment

The attention of scientists from the Geophysical Institute of the Academy of Sciences of the Czech Republic will be focused north of Cheb over the next year and a half. In cooperation with Czech and German colleagues, they will deploy 300 seismic instruments over an area of 10,000 km2 and will measure even the weakest microearthquakes. In a large-scale seismic experiment, they want to better understand why earthquake swarms occur in an area that is far from typical earthquake sources.

On the border of northwestern Bohemia and the German Vogtland, a series of earthquakes – earthquake swarms – have occurred from time to time. For an area located far from the interface of tectonic plates and active volcanic systems, this is a very unusual phenomenon. Earthquake swarms usually accompany volcanic eruptions, as is the case, for example, in Iceland.

Planned locations of seismic stations shown by blue triangles. Earthquake epicenters are marked by colored dots

However, the causes of the unusual swarm character of earthquake activity and the coincidence of several other phenomena (see below) are still not satisfactorily explained. The scientific community agrees that this is a consequence of magmatic processes in the lower crust and mantle of the Earth.

Why are there earthquake swarms in the Cheb region? ELISE answers

In order to advance the knowledge of the structure of the area of interest and the processes that occur below the surface, the Geophysical Institute of the Academy of Sciences of the Czech Republic (GFÚ AV ČR) will carry out a large-scale seismological experiment together with Czech and German universities and research institutions. The name ELISE is an abbreviation for Eger Large Seismic Experiment (i.e. a large-scale seismic experiment in the Cheb region). The experiment is mostly financed by the collaborating Helmholtz Centre for Geosciences (GFZ), but is also supported by the Dynamic Planet Earth program of the AV21 Strategy.

“Over the course of 12 to 18 months, almost 300 seismic devices will be deployed over an area of approximately 100 × 100 km2. The highly sensitive sensors are borrowed from the GFZ’s geophysical measurement equipment pool, the so-called GIPP – Geophysikalischer Gerätepool Potsdam. They will record ground tremors caused by earthquakes and CO₂ emissions, but also, of course, by traffic or industry,” says Jakub Klicpera from the Geophysical Institute of the Czech Academy of Sciences, technical coordinator of the experiment on the Czech side.

A sample of seismic station equipment with a geophone (yellow box), a digitizer (gray-black device) and a dry alkaline battery, which is used for electric fences and does not contain lead, mercury or cadmium (green block). The geophone is completely buried underground, the batteries and digitizer are located in a box partially hidden underground. The protective box protrudes about 5 cm above the surface.

The existing coverage of the area with seismic stations will therefore be significantly increased during the experiment.

“We expect that with so many stations we will be able to detect and study even the weakest micro-earthquakes that would otherwise remain hidden from us. In the central zone of the area of interest, the seismometers will be only about 2 km apart, which will allow for a very detailed analysis of earthquakes and the structure of the Earth’s crust. However, it should be added that the results will also be greatly influenced by the (un)favorability of nature – if seismic activity is significant at a given time, we will obtain more data for our analyses than in the case of a quiet period,” says Jana Doubravová from the GFÚ AS CR.

Scientists from the aforementioned institute are working on the experiment with the GFZ (GeoForschungsZentrum) in Potsdam, the universities of Potsdam, Leipzig, Freiberg, Jena, Munich, Erlangen and Münster, the Saxon Geological Survey, the Faculty of Natural Sciences of Charles University and the Institute of Rock Structure and Mechanics of the AS CR.

Earthquake swarms, carbon dioxide and young volcanoes

An earthquake swarm consists of up to thousands of micro-earthquakes and weak earthquakes that occur in rapid succession over a period of weeks to months, without a strong main earthquake occurring. The last strong earthquake swarm occurred in 2024 near Kligethal and Bublava, in a zone that was very active, among other things, 125 years ago. It was the increased seismic activity at the end of the 19th and beginning of the 20th centuries that prompted observers and researchers at the time to introduce the now commonly used term “earthquake swarm” for a series of earthquakes. The WEBNET seismic station network has been operating in the area of interest on the Czech side since the 1990s, and several stations are also located in neighboring Bavaria and Saxony.

In addition to repeated earthquakes, the locality is exceptional for its high carbon dioxide (CO₂) content in mineral springs and the occurrence of mofettas – dry carbon dioxide eruptions. CO2 comes from the Earth’s upper mantle, i.e. from a depth of more than 30 km. The area also contains the youngest volcanoes in our territory, which were active “only” 200 to 300 thousand years ago – Komorní Hůrka near Františkovy Lázně, Železná Hůrka near Cheb and the remains of several explosive craters – maars, discovered only a few years ago with the participation of experts from the Geophysical Institute of the Academy of Sciences of the Czech Republic.

(Press release of the Academy of Sciences of the Czech Republic)