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Onset of diking recorded by pressure spikes in geothermal groundwater monitoring wells in Svartsengi geothermal area, SW-Iceland

Catherine R. Gallagher1, Lárus Þórvaldsson1, Lilja Magnúsdóttir1, Michelle M. Parks2, Magnús Tumi Guðmundsson3, Hannah Iona Reynolds3, Sara Barsotti2, Benedikt G. Ofeigsson2, Kristín Jóndóttir2, Krístín Vogfjorð2, Vincent Drouin2, Hildur M. Friðríksdóttir2,  Birgir V. Óskarsson4, Joaquín M-C Belart4, Robert A. Askew4, Sydney R. Gunnarson4, Hanna Blanck1, Alma G-H. Williams1, William C. Wenrich1, Kiflom Gebrehiwot Mesfin1, Valdís Guðmundsdóttir1.

  • Affiliations: 1HS Orka, Svartsengi, 241 Grindavík, Iceland; 2The Icelandic Meterological Office, Reykjavík, Iceland; 3The Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, Reykjavík, Iceland; 4The Natural Science Institute of Iceland, Kópavogur, Iceland 

  • Presentation type: Poster

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

  • Poster Board Number: 166

  • Programme No: 3.1.58

  • Theme 3 > Session 1

Abstract

On 10-11 November 2023, a 15 km long, 130 M m3, SW-NE-trending dike was emplaced into the crust, extending from the center of the peninsula, underneath the town of Grindavík and off the south coast of Iceland. This event occurred in the Svartsengi volcanic system, on the Reykjanes Peninsula, SW Iceland, fed by a shallow magma storage domain that has been inflating. This event was captured in real-time by an immediate, real-time sharp spike of >300 kPa in pressure readings in geothermal groundwater monitoring wells of the nearby Svartsengi geothermal system, operated by HS Orka. This was the first time an event like this had ever been captured in real-time using the signal detected by down-borehole pressure sensors.  Each of the 9 subsequent, smaller, diking events utilized the pathway established on 10-11 November, with 7 resulting in eruptions. All of them generated distinct rapid pressure increase signals of 20-150 kPa in the monitoring wells. The strength and morphology of each pressure signal correlates directly with the estimated dike volumes, median opening, and location along the November weakness.  Detection of the start of a dike propagation, in real-time, has enabled a high degree of temporal and spatial monitoring, and the development of an additional early warning system by HS Orka, used by Veðurstófan and Almannavarnir. This setup will be utilized for future events at this location, but could also be implemented in other locations around the globe where groundwater boreholes exist within or in close proximity to an active volcanic system.