Icecap and Subglacial Crustal Deformation Inferred From SAR Pixel Tracking: The 2014 Dike Intrusion Episode in the Bárðarbunga Volcanic System, Iceland

Abstract

Bárðarbunga is an active volcano beneath the Vatnajökull icecap in Iceland, where a subglacial dike intrusion occurred in 2014. This area has been studied with interferometric synthetic aperture radar, an important geodetic method that measures crustal deformation; however, ice/snow cover on volcanoes impedes the mapping of crustal deformation because of decorrelation problems. Previous geodetic observations have reported deformation signals at ice‐free regions of a major dike formed in 2014 in the Bárðarbunga volcanic system, but direct observations of the subglacial crustal deformation associated with the dike intrusion have been limited. We applied a pixel tracking approach to various satellite synthetic aperture radar (SAR) data over the northern part of the Vatnajokull icecap and the Holuhraun plain. The pixel tracking data revealed not only crustal deformation fields in the ice‐free region of the magma intrusion, which covers only about 20% of the entire length of dike, but also icecap surface movements over the subglacial part of the dike in the ablation area of the Vatnajökull icecap. Signals above the icecap, suggesting subsidence due to subglacial graben formation, are consistent with the dike propagation path inferred from seismicity during the episode. By subtracting the scaled pre‐diking signals from the co‐diking signals, we corrected for the steady‐state icecap flow signals to derive the subglacial crustal deformations. We showed that the inferred subglacial crustal deformation signals can significantly contribute to the improvement of dike opening/faulting distributions. Applying the pixel tracking to satellite images will enable mapping subglacial crustal deformation in the case of subglacial volcanic activity.

Rift-parallel block-like motion of the graben floor during the 2005–2010 Afar rifting episode

“…However, no similar rift-parallel horizontal displacements were reported in the 2005-2010 Afar rifting event, and the frequency and universality of the rift-parallel movements remain uncertain. Similar horizontal displacement on a graben floor was reported by Ruch et al (2016) in the Bárðarbunga dike intrusion episode in 2014 in Iceland; see also Himematsu et al (2019). They proposed that the symmetric horizontal displacements toward a minor fissure on the graben floor can be explained by the accommodation of shear strain caused by oblique plate spreading.…”

“…In the 2014 Bárðarbunga dike intrusion episode, the rift axis was orientated at N25E, while the plate spreading around Bárðarbunga volcano is for the N104E, which is not completely perpendicular to the rift axis. Although most of the graben was located under an icecap (Himematsu et al, 2019), their observation results of Ruch et al (2016) exhibited symmetrical horizontal displacements in the direction of the rift axis toward the area of maximum subsidence on the ice-free graben floor, indicating southward movements on the northern part of the ice-free graben floor and northward movements on the southern part of this region. For the temporal evolution of the displacement on the graben floor in Bárðarbunga, the increase of the SAR azimuth offset on the graben floor ceased in association with the decrease of seismic activity and the termination of graben evolution.…”

The utility of TerraSAR-X, TanDEM-X, and PAZ for studying global volcanic activity: Successes, challenges, and future prospects

“…Pixel offset has a lower sensitivity to deformation than InSAR, but it does not suffer from phase aliasing in zones of large strain [Casu et al 2011;Shreve and Delgado 2023]. This technique has been used on TSX data to detect displacements (also in areas where InSAR failed) in volcanoes like Bárðarbunga (Iceland), Bezymianny (Russia), Merapi (Indonesia) and La Soulfière St. Vincent [Ruch et al 2016;Himematsu et al 2019;Mania et al 2019;Dualeh et al 2023;Walter 2023]. All these methods based on amplitude data testify to the importance of having high-resolution SAR data (such as TSX/TDX/PAZ data) acquired at volcanoes at a small temporal baseline to calculate topographic change and displacements during, before, and after eruptions.…”