Crustal deformation in the Krísuvík geothermal area

Krísuvík is a volcanic system with a high-temperature geothermal area located in the central part of the Reykjanes Peninsula, SW Iceland. The area is seismically very active with the largest earthquakes (M 5-6) associated with a system of N-S trending, right-lateral strike-slip faults. In early 2009 GPS measurement at a continuous station KRIV suggested inflation of the Krísuvík geothermal area, which was then confirmed by ENVISAT interferometric synthetic aperture radar (InSAR) data. The uplift episode continued until fall of 2009 when the area began to subside reaching the pre-inflation state in early spring 2010. In April 2010 another uplift episode started.

Seismic activity in the Krísuvík area in last three years has been reflecting the ongoing deformation character, more frequent earthquakes were recorded during the inflation periods while fewer during the deflating phase. In late February 2011 a seismic swarm occurred in Krísuvík with eight events of magnitude exceeding 3, many felt in Reykjavík. The largest (M 4.2) occurred on 27 February and was located just west of lake Kleifarvatn. The earthquakes lineate a N-S trending structure and coseismic GPS displacements suggest right lateral rupture on a N-S trending strike-slip fault. On 1 March 2012 a swarm of earthquakes of magnitudes up to M 3.9 stroke near Helgafell, NE of the inflating area.

Objectives of this project is to monitor the Krísuvík area closely by continuous and campaign GPS measurements and InSAR interferometry. The deformation registered by the GPS stations suggests an inflation source at 4-5 km depth located beneath Sveifluháls area, with uplift rates exceeding 50 mm/yr at stations closest to the inflation center, just north of Seltún geothermal area. TerraSAR-X images (in both ascending and descending orbits) have been acquired during the latest inflation period showing the extent of the uplift. In addition to geodetic data repeated gravity measurements will be used to help constraining the nature of the source and its depth. Precise gravity measurements on numerous sites were performed in June 2010. In March 2011 measurements were conducted along a profile crossing the estimated inflation center. In June/July 2011 majority of the sites in the network were remeasured.