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| Titel |
The 2008 earthquakes in the Bavarian Molasse Basin - possible relation to deep geothermics? |
| VerfasserIn |
T. Kraft, J. Wassermann, N. Deichmann, S. Stange |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250028567
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| Zusammenfassung |
| We discuss several microearthquakes of magnitude up to Ml=2.3 that occurred in the
Bavarian Molasse Basin (ByM), south of Munich, Germany, in February and July 2008. The
strongest event was felt by local residents. The Bavarian Earthquake catalog, which dates
back to the year 1000, does list a small number of isolated earthquakes in the western part of
the ByM as well as a cluster of mining induced earthquakes (Peißenberg 1962-1970,
I0(MSK)=5.5). The eastern part of the ByM, including the wider surrounding of Munich, was
so far considered aseismic.
Due to the spatio-temporal clustering of the microearthquakes in February and July 2008
the University of Munich (LMU) and the Swiss Seismologcical Service installed a temporal
network of seismological stations in the south of Munich to investigate the newly arising
seismicity. First analysis of the recorded data indicate shallow source depths (~5km) for the
July events. This result is supported by the fact that one of these very small earthquakes was
felt by local residents. The earthquakes hypocenters are located closely to a number of deep
geothermal wells of 3-4.5km depth being either in production or running productivity tests in
late 2007 and early 2008. Therefore, the 2008 seimicity might represent a case of induced
seimicity related to the injection or withdrawal of water from the hydrothermal
aquifer.
Due to the lack of high quality recordings of a denser seismic monitoring network in the
source area it is not possible to resolve details of the processes behind the 2008 seismicity.
Therefore, a definite answer to the question if the earthquakes are related the deep
geothermal projects or not can not be given at present. However, a number of recent
well-studied cases have proved that earthquakes can also happen in depths much
shallower than 5km, and that small changes of the hydrological conditions at depth are
sufficient to trigger seismicity. Therefore, a detailed understanding of the causative
processes behind the 2008 seismicity in the ByM is of paramount importance to hazard
assessment and mitigation associated with similar geothermal projects underway
elsewhere.
A close cooperation of operators and developers of geothermal projects with earthquake
science has proved to be very beneficial in the development of the Hot-Dry-Rock technique
and is also highly desirable in developing strategies for the save geothermal use of deep
hydrothermal aquifers. |
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