Ground deformation induced by geothermal utilization at Reykjanes, SW-Iceland, inferred from interferometric analysis of Sentinel-1 Synthetic Aperture Radar images (InSAR)

• Main Author: Receveur, Mylène, 1994-
• Other Authors: Háskóli Íslands
• Format: Thesis
• Language: English
• Published: 2018
• Subjects: Jarðfræði; Reykjanes; Iceland
• Online Access: http://hdl.handle.net/1946/30458

The Reykjanes geothermal system is a high-temperature seawater system situated at the southwestern tip of the Reykjanes Peninsula, SW-Iceland. Data from Sentinel-1A and 1B satellites have been used to evaluate ground deformation induced by geothermal utilization between April 2015 and October 2017, using Interferometric Synthetic Aperture Radar (InSAR) methods. Cumulative near-vertical and near-east displacements were inferred by stacking and combining two-year interval interferograms formed from SAR images acquired from ascending and descending orbits. Velocity maps were generated for each track from time series analysis of the displacement of coherent pixels, revealing a steady subsidence within a sub-circular bowl centered on the well field, together with horizontal contraction towards the deformation center. The maximum rate of change is about 16 mm/yr in the satellite line-of-sight. The characteristics of the deforming source were inverted using analytical models assuming the geothermal reservoir behaves as a pressure source embedded in an elastic half space. The best fit was obtained for penny shaped and sill-like sources at about 1 km depth contracting at a rate of -0.09 million cubic meters per year. This inferred volume change was compared to estimations of the expected amount of contraction of rock under pressure and temperature decline measured at 900 m depth in boreholes in the geothermal field. Considering the geological structure of the reservoir, it is suggested that the observed deformation results from a combination of compaction and thermal contraction caused by lack of steam recharge within a steam zone in the upper-most part of the geothermal reservoir. Jarðhitakerfið á Reykjanesi, yst á Reykjanesskaganum, er háhitakerfi með jarðhitavökva sem er sjór að uppruna. Gögn frá Sentinel-1A og 1B gervitunglunum voru notuð til að meta jarðskorpuhreyfingar á svæðinu vegna jarðhitavinnslu frá apríl 2015 til október 2017, með bylgjuvíxlmælingum á ratsjármyndum úr gervitunglunum. Heildarbreyting var ...