Induced seismicity related to geothermal projects versus natural tectonic earthquakes and other types of induced seismic events in Central Europe

Abstract

Induced seismicity related to fluid injection in geothermal systems has gained an increased public awareness particularly in Central Europe. The paper discusses occurrence of induced seismic events at sites of geothermal projects in comparison to natural tectonic earthquakes and other types of induced or triggered seismicity in Central Europe (i.e. in Germany and adjacent areas). Other types of induced events are those in areas of mining or exploitation of coal, salt and potash, hydrocarbon and ores. Furthermore, induced seismicity in connection with water reservoirs and intense precipitation in areas of karst geology is also discussed. The subject of this study is the induced seismicity of a data set of moment magnitudes 2.0, while the distinct larger natural seismicity is displayed for 2.5. Parameters of the strongest seismic events of all studied sources of seismicity are listed, presented in epicentre maps, and discussed with respect to their maximum observed magnitudes and their frequency-magnitude distributions. Macroseismic intensities of strongest seismic events at geothermal project sites are compared to data of an intensity based probabilistic seismic hazard map for Germany. The general conclusion is that observed induced seismicity at geothermal sites is minor in comparison to other sources of seismicity.

The probabilistic seismic hazard assessment of Germany—version 2016, considering the range of epistemic uncertainties and aleatory variability

“…The specificity and transparency of descriptions in Grünthal et al (2009a), how these catalogues for the study area were created, enable users to produce further temporal extensions as well as those with respect to lower magnitude thresholds where local sources provide such data. We employ here the temporal extension up to 2014 and the lower threshold of M w = 2.0 as already applied and described in Grünthal (2014) and Stromeyer and Grünthal (2015).…”

“…Applications of time-dependent approaches to PSHA in the study area are strongly limited due to the short observation time of earthquakes with respect to the low level of seismicity. Similarly, induced seismic events in the target area (Grünthal 2014) are not considered here, since they are related to human activities in the underground and follow other principles than the natural tectonic earthquakes.…”

Analysis of induced seismicity in geothermal reservoirs – An overview

“…Geothermal sites in the Rhine Graben near Basel , Landau (Grünthal, 2014) and Soultz-sousForêts (Dorbath et al, 2009), however, have experienced 2.5 events due to EGS activities (Table 1). Although this seismicity has been short lived it has attracted public concern due to its proximity to populated areas (Kraft et al, 2009).…”

“…Here, we discuss LME in relation to pore fluid pressure, injected volume and in the context of fault and reservoir size. Note that Grünthal (2014) replaces the term LME by SEECo, seismic events of economic concern. In Section 4, the maximum observed magnitude of EGS seismicity is compared to the maximum expected magnitude estimated from fault-scaling relationship, deterministic fracture models, probabilistic approaches and empirical laws.…”

Forward induced seismic hazard assessment: application to a synthetic seismicity catalogue from hydraulic stimulation modelling

“…This so-called hydraulic fracturing is well known since the fundamental paper of Hubbert and Willis (1957) has been applied widely. However, in the past decades, the accompanying induced seismicity became a problem not only at geothermal reservoirs but also in connection with other types of underground mining activities such as hydrocarbon exploitation, as well as potash and coal mining (Evans et al 2012;Majer et al 2007Majer et al , 2012Grünthal 2013;Suckale 2009Suckale , 2010. In particular, in Europe, the induced events at the geothermal site in Basel (Switzerland) related to fluid stimulation ( 3.2 in 2006; Häring et al 2008;Deichmann and Ernst 2009;Deichmann and Giardini 2009) and in Landau (Germany) due to a shut-in in the production phase ( 2.6 in 2009;Grünthal 2013) were the nucleus of an intense and ongoing discussion since both sites are situated in the suburb of the respective cities.…”