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Ground deformation 2012-2015 in the Hengill geothermal area
Daniel Juncu¹, Thóra Árnadóttir¹, Andy Hooper², Gunnar Gunnarsson³
¹Nordic Volcanological Center, Instiute of Earth Sciences, University of Iceland
²COMET, School of Earth and Environment, University of Leeds
³OR – Reykjavik Energy
The Hengill area
• 2 power plants
Nesjavellir operating since 1990–
– Hellisheidi operating since 2006
• Volcanic history
–
–
Last eruption ca. 2000 years BP
Intense seismic activity and uplift 1994-1998
• Plate junction
– Intersection of Reykjanes Ridge, South
Iceland Seismic Zone and Western Volcanic
Zone
Measuring ground
motion• GPS
–
–
61 campaign stations measured
annually by IES and in 2012 by ÍSOR
5 continuous stations operated by IMO
• InSAR
–
–
TerraSAR-X
Between 1-3 images per year of the
whole area
Surface velocities 2012-2015
Correction for
plate motion after
Árnadóttir et al.
(2009)
Subsidence in geothermal areas: ΔP or ΔT?
Modelling the deformation
•
•
Elastic half-space models to
simulate the elastic response of
the rock to pressure change
Fix observed ΔP and use non-
linear optimization to find the
remaining source parameters
Yang et al. (1988)
Results
•
•
Hellisheidi: ~ 0.5 – 3 km depth
Nesjavellir: ~ 1 – 3 km depth
Contraction source in eastern
Hengill: ~7 km depth
Summary
• Hellisheidi and Nesjavellir subside ~1-2 cm/yr
• Observed pressure decrease can explain the
surface deformation
• Regional deformation has to be taken into
account
Takk!