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Stress interactions, faulting and sustainability at high-temperature geothermal systems: Implications from recent unrest in Svartsengi, SW-Iceland

Halldór Geirsson 1, Shaozhuo Liu2, Sigurjón Jónsson2, Áslaug Gyða Birgisdóttir1, Freysteinn Sigmundsson1, Michelle Parks3, Vala Hjörleifsdóttir4, Lilja Magnúsdóttir5, Nathaniel Wire1

  • Affiliations: 1Institute of Earth Sciences, University of Iceland, Reykjavik, Iceland; 2King Abdullah University of Science and Technology, Thuwal, Saudi Arabia; 3Icelandic Meteorological Office, Reykjavik, Iceland; 4Reykjavik University, Reykjavik, Iceland; 5HS-Orka, Reykjanesbær, Iceland

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 54

  • Programme No: 2.3.40

  • Theme 2 > Session 3

Abstract

Geothermal production, including fluid extraction and re-injection, causes changes in crustal stresses and fluid pressures. These changes are well known to affect nearby seismicity and local fault movements, but can also affect dike propagation, dike arrest, and growth of magma chambers. The current unrest in Svartsengi, including several eruptions, high magma flow rates, and extensive surface faulting, occurs in an area where geothermal production in a high-temperature area has been ongoing since the 1970s with cumulative subsidence nearing 1/2 m. We calculate stress changes due to the long-term geothermal production, specifically focusing on normal stress changes affecting dike pathways. We find that contraction in the geothermal reservoir creates increased vertical tensional stresses below the reservoir, facilitating sill formation or magma accumulation, and thus capturing future heat source for the geothermal system in a sustainable way. The geothermal contraction also acts to increase horizontal tensional stress along the reservoir periphery while compressing the rocks above the reservoir, increasing probability of dikes reaching the surface along the sides of the geothermal system - i.e. towards the Sundhnúkar crater row. Plate boundary stresses, crustal structure, and magma pressures also play important roles in dike propagation and arrest. Our study showcases anthropogenic effects on magma propagation, and how geothermal energy production intrinsically has a self-sustainable component.