[S02-P] Poster

[S02-P-11] Induced seismicity in the region of the geothermal power plant at Insheim (central Upper Rhine Graben, SW Germany)

Andrea Bruestle¹, Margarete Pilger¹, Thomas Plenefisch², ^○Ulrich Wegler³, Bernd Schmidt⁴ (1.Germany, 2.BGR, Hannover, Germany, 3.Universitaet Jena, Germany, 4.Geological Survey of Rhineland-Palatinate, Mainz, Germany)

The Upper Rhine Graben is the region with the highest temperature gradient in Germany. Since 2012 at Insheim a geothermal power plant is running in the central Upper Rhine Graben. It is accompanied by small to moderate induced seismicity. Before starting regular operation, hydraulic stimulation in April 2010 caused two seismic events of ML 2.2 and 2.4, which were felt by inhabitants. As a consequence the local seismic monitoring network of the company was improved by an additional scientific network within the research-projects MAGS and MAGS2. The densified seismic network of up to 14 surface stations is operated by the Federal Institute for Geosciences and Natural Resources BGR. The network was completed over time by 4 borehole stations, operated by the Local Seismological Survey of Rhineland Palatine LER and industrial partner. The event detection was done by a real-time cross correlation detector, which was developed as a SeisComP3-plugin. The network extension of less than 20 km made a standard determination of the local magnitude impossible. Therefore a relative magnitude was determined from the amplitude of master and detected events. The local 1D-velocity model was improved using VELEST. Corresponding station corrections are in accordance to the tectonic situation in the graben structure. Since the commissioning of the power plant in October 2012 about 810 events were identified and analyzed. As the area is densely populated the seismic background noise varies strongly resulting in a magnitude of completeness of 0.0 during the day and -0.4 during nighttimes. No seismicity is observed when the power plant is offline during maintenance periods. After recommissioning seismic activity is temporarily increased followed by a continuous decrease to a low activity level. Seismicity is located within the crystalline basement, which underlies the sedimentary graben fill. Focal mechanisms show the same major strike-direction as the local tectonic situation.