Long-Term Geodetic Measurements at the Most Active Volcanoes in Iceland: Role of Interferometric Synthetic Aperture Radar and GPS in Hazard Monitoring at Hekla, Katla, Eyjafjallajökull and Askja Volcanoes

Abstract:

Integrating geodetic measurements from both ground based and satellite observations is crucial to improved monitoring and evaluation of volcanic hazards in Iceland. The focus of our deformation team is to generate and interpret an extended time series of high resolution deformation measurements derived from InSAR and GPS observations, in the vicinity of the most active volcanoes in Iceland: including Hekla, Katla, Eyjafjallajökull and Askja. A comprehensive network of ground-based deformation monitoring equipment is already deployed at several of these volcanoes and a series of campaign GPS measurements are routinely undertaken each summer. InSAR observations are complementary to these field based measurements and their high spatial resolution assists in resolving the geometry and location of the source of the deformation.

Iceland has recently been declared a Permanent Geohazard Supersite by the Committee on Earth Observation Satellites, based on its propensity for relatively frequent eruptions and their potentially hazardous, long ranging effects. The recent Supersite award ensures a considerable amount of SAR data is made available for both past and future satellite acquisitions, including new X-band images (acquired by TerraSAR-X and Cosmo-SkyMed satellites), and historic C-band images (from ERS and ENVISAT satellites). We present long-term deformation time-series spanning > 20 years for Hekla, Katla, Eyjafjallajökull and Askja volcanoes, based on a variety of geodetic techniques including InSAR, GPS and tilt measurements.

InSAR and tilt measurements at Hekla indicate renewed melt supply to a sub-volcanic reservoir after the last eruption in 2000. Although InSAR and GPS observations at Katla volcano (between 2001 and 2009) suggest no indication of magma induced deformation outside the ice-cap, it is possible that a small flood at Mýrdalsjökull in July 2011, followed by an increase in micro-seismic earthquakes, was related to magmatic activity. Post-eruption deformation observations reveal inflation at Eyjafjallajökull, possibly related to the influx of new melt or readjustment of crustal stresses following the 2010 eruption. Continued deflation at Askja caldera since 1983 may have contributed to crustal weakening and the triggering of a major rockslide and tsunami on the 21 July, 2014.