| Title | Induced Seismicity during Reinjection of Wastewater in Hellisheidi Geothermal Field, Southwest Iceland |
|---|---|
| Authors | Kristjansdottir, S; Agustsson, K; Gudmundsson, O; Tryggvason, A; Lund, B; Fehler, M |
| Year | 2016 |
| Conference | European Geothermal Congress |
| Keywords | Injection, geothermal field, induced seismicity, relative relocation |
| Abstract | In 2011 a new injection field was taken into operation for the Hellisheidi Power Plant in southwest Iceland. The power plant stands on the edge of the Hengill geothermal area and produces 303 MWe and 133 MWth. It started operation in 2006 and the company is required by law to inject wastewater back into the ground. Shortly after the injection started in 2011 the seismicity increased, with thousands of events being recorded by the Icelandic Meteorological Office. The majority of events were small (Ml < 3.0), but the two largest events reached Ml 3.8 and were widely felt in the area. An increase in seismicity had also been detected during the drilling of the injection wells, associated with the loss of drilling fluid. The area is located close to the triple junction of an oblique spreading zone (Reykjanes Peninsula), a rift zone (the Western Volcanic Zone) and a transform (the South Iceland Seismic Zone) and is naturally seismically active. The seismic events were recorded by a dense network of seismographs operated in the area by Uppsala University, MIT, Reykjavik University, the Icelandic Meteorological Office, and Iceland GeoSurvey from 2009 to 2013. By grouping the waveforms into families based on their similarity and using cross correlation we can both find more events than have previously been located and get precise time measurements allowing us to locate the earthquakes with more accuracy. By comparing seismic activity with the injection process we hope to get a better understanding of the forces at work. |