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Seismic events in relation to the use of deep geothermal energy
Better safe than sorry
Within the last 25 years of deep geothermal exploitation in the Bavarian Molassebasin, there has not been any documented damage, caused by ground motion
Any ground vibrations that may have occurred (induced seismicity) can in all probability only be detected by measuring instruments.
According to current scientific evidence, the risk of ground vibrations for buildings near geothermal production plants is no greater than the risk that comes with storms, hail or other hazards.
Safe is safe and remains safe
As a geothermal- energy operator, we do everything scientifically and technically possible to keep it that way. Because we take our responsibility for the energy transition and the people in the region seriously.
Our guideline explains what to do in the unlikely event of ground vibration (induced seismicity), which would usually occur in the field of so-called microseismicity.
The seismic monitoring network of geothermal operators in the greater Munich area
Ground vibrations can be triggered by pressure changes in the subsurface due to the extraction or re-injection of geothermal water as well as by the release of cooled thermal water back into the hot subsurface, which in all cases can lead to the release of existing rock stress.
Even if this microseismicity does not normally cause a major risk to buildings, as with any human impact in nature and any type of energy generation, there is never 100% certainty.
Observation of seismic activity using the seismic monitoring network
For many years, the Bavarian Earthquake Service has maintained an interregional network of seismic measuring stations. This network is operated on request of the Ludwig Maximilian University of Munich at the Geophysical Observatory in Fürstenfeldbruck.
This network is relatively loose and is generally not sufficient for close monitoring of seismic activity in the area of geothermal plants. According to the Federal Mining Law, however, it must be possible to clearly assign a seismic event to a field owner and so their responsibility for liability.
In order to fulfil these requirements and for reasons of transparency of the mainly communally owned geothermal plants, the operators of the plants in the Munich area have committed themselves in 2019 to establish an extended network under their own management and responsibility. This extended measuring network was set up in the years 2020 - 2022 and will be successively expanded as new plants are built (see Fig. 1).
Fig. 1: Munich sub-network - earthquakes in Bavaria (source: www.erdbeben-in-bayern.de)
All measurement data from this monitoring network is available to the earthquake service in real time and unfiltered. They are available on the website of the Bavarian Seismological Service (see Fig. 2).
Fig. 2: Live data from Unterhaching station seismograms (source: www.erdbeben-in-bayern.de)
The monitoring network ensures complete documentation of all seismic events in the monitoring area from magnitude MI = 1.0 according to the Richter scale, still far below the level of 2.0 - 2.5 at which the first vibrations can be felt by humans. In this sensitive environment, the geothermal operators in the Munich area help to ensure transparency towards the public with this measuring network.
Note: The Richter scale is a logarithmic scale. This means that to initiate a jump from magnitude level 1.0 to 3.0, 1000 times the energy is required at the epicentre.
Even if the word earthquake is quickly used in reporting, science or even in common speech, in almost all cases these are events that are not noticed by humans.
None of the quakes or microquakes observed in the areas of geothermal plants so far have actually caused damage to buildings.
Example images of a seismic measuring station
Guidelines for communication in the incident case
The operator and the seismological service have agreed that the seismological service has the authority to communicate with the public.
The responsibility for assigning an event to a field owner (and therefore any necessary definition of an impact area for the vibration) lies with the mining authority, based on scientific data and evaluations by the seismological service. It is also the responsibility of the mining authority to remove any previously defined preventive impact area.
It is important that all reports of perceptions from the public are submitted only using the form provided by the seismological service. This form is internationally standardized and helps to exactly define the intensity of the event.
Operators of deep geothermal plants must be properly insured against mining damage. Communal operations are generally covered to an unlimited extent by the communal liability insurance.