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Seismicity patterns and their source regions at Krafla (N-E Iceland)

Elisabeth Glück1 , Joe Carthy2, Stephane Garambois1, Jean Vandemeulebrouck1, Carmen Benitez2, Egill A. Gudnason3, Anette K. Mortensen4

  • Affiliations: 1 ISTerre, Universite Savoie Mont Blanc/Universite Grenoble Alpes, France  2 Universidad de Granada, Spain  3 ISOR, Iceland GeoSurvey, Kopavogur, Iceland 4 Landsvirkjun, Reykjavik, Iceland

  • Presentation type: Talk

  • Presentation time: Tuesday 09:15 - 09:30, Room S160

  • Programme No: 5.1.4

  • Theme 5 > Session 1

Abstract

Krafla is one of the five central volcanoes of the Northern Volcanic Zone in north-east Iceland and has been utilised for decades for geothermal energy production. Thus, the volcano and its geothermal system have been monitored and imaged extensively with various geophysical methods to better understand this complex geological setting scientific and also industrial interests. With a ten-year dataset of 30.000 manually picked seismic events from a local permanent 12 station seismic network owned by Landsvirkjun and operated by Iceland GeoSurvey, and a very dense temporary array of 98 seismic nodes deployed for one month in 2022 in the center of Krafla caldera, we imaged P- and S-wave velocity structures of the volcano by using local earthquake tomography and analysed the relocated seismicity patterns. To decipher if these events can be attributed to different sources, we use an unsupervised machine learning approach to cluster the events based only on the polarity of the P-onset, to make sure that effects related to different propagation paths in the clustering are minimized. With this approach, events originating from diffuse seismicity clouds can be attributed to different sources, using existing focal mechanisms, available GPS data and variations in the re-injection rates at wells of the geothermal powerplant. By applying this method to the ten-year data set, we hope to gain a better understanding of when and where structures are active, and thus offer insights if volcanic forcing such as inflation/deflation or external forcing such as regional seismicity and anthropogenic influence trigger certain seismicity patterns.