GEUS monitors for seismic signals

Published 28-09-2022

As previously announced, GEUS’ seismographs have registered seismic signals in the Baltic Sea, which correspond with the gas leakages from Nord Stream 1 and 2. This was discovered and reported Tuesday morning as part of the routine monitoring. GEUS monitors for additional seismic events.

GEUS has eight seismographs in Denmark, which are placed as shown on the map. Illustration: GEUS

GEUS has 10 seismographs in Denmark, which register seismic events in the shape of shakings. In addition, GEUS collaborate with other countries, which gives access to data from other countries’ seismographs.

Normally, GEUS seismologists look through the seismic data from the day before (midnight UTC until midnight UTC) on a daily basis from both GEUS’ own stations as well as a selection of Swedish and Norwegian stations.

If the seismologists discover potential events in the data, these are subsequently analysed. If the seismologists discover something unusual or are contacted by e.g. citizens, who have noticed tremors, the seismologists will typically analyse these events immediately.

The discovery and orientation

In connection with the daily screening on Tuesday 27 September of seismic data from the day before, GEUS’ seismologists first discovered the seismic event that occurred at 02:03 AM on Monday 26 September and then the seismic event that occurred at 07:03 PM on Monday 26 September. After both the first and the second discovery the Ministry of Climate, Energy and Utilities was immediately notified and so were other relevant parties.

24 hour monitoring

Under normal circumstances, there are no seismic events in Denmark that require monitoring 24 hours a day, but because of this extraordinary situation, GEUS has been monitoring for seismic events 24 hours a day since the morning Tuesday 27 September and will continue to do so for the time being.

If the seismologists register an irregularity, defined as a tremor that is not estimated to be a natural earthquake, GEUS will immediately contact the National Operational Staff (NOST) and the Ministry of Climate, Energy and Utilities.

The two seismic events

As previously announced, GEUS’ seismographs registered the two seismic events in the Baltic Sea early morning Monday 26 September at 02:03 am Danish summer time and again Monday 26 September 7:03 pm Danish summer. The time and location of both events match the time and location for the gas leakages from North Stream 1 and 2.

The signals are recorded on GEUS’ two seismographic stations on Bornholm, the station on Stevns as well as on Swedish and German stations.

The first event registered 2.3 on the Richter scale, the second 2.1 on the Richter scale. The signals do not resemble signals from earthquakes. They do resemble the signals typically recorded from blasts.

The Geological Survey of Denmark and Greenland (GEUS) is responsible for monitoring and locating earthquakes and other seismological events in Denmark and Greenland.