Current plate movements across the Mid‐Atlantic Ridge determined from 5 years of continuous GPS measurements in Iceland

Geirsson, H.; Árnadóttir, Þóra; Völksen, Christof; Jiang, Weiping; Sturkell, Erik; Villemin, Thierry; Einarsson, Páll; Sigmundsson, Freysteinn; Stefánsson, Ragnar

doi:10.1029/2005jb003717

Cited by 85 publications

(97 citation statements)

References 46 publications

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“…Iceland is subject to regional forces that pull apart the western Atlantic plate from the eastern Atlantic plate (Oskarsson et al, 1985;Sigmundsson, 2006). The observed velocity of spreading across the northern rift zone is 18.1 ± 1.2 mm/yr in direction N109.3 • ± 4.2 • consistent with plate models (Sella et al, 2002;Geirsson et al, 2006). The elastic strain accumulates in the crust until it is released by coseismic faulting and/or by dyke intrusion.…”

Section: Role Of Magma Intrusionssupporting

confidence: 48%

Interaction between Transform Faults and Rift Systems: A Combined Field and Experimental Approach

2016

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We present a detailed field structural survey of the area of interaction between the active NW-striking transform Husavik-Flatey Fault (HFF) and the N-S Theystareykir Fissure Swarm (TFS), in North Iceland, integrated by analog scaled models. Field data contribute to a better understanding of how transform faults work, at a much higher detail than classical marine geophysical studies. Analog experiments are conducted to analyse the fracture patterns resulting from different possible cases where transform faulting accompanies or postpones the rift motions. Different tectonic block configurations are also considered and results are compared with field data in order to study as thoroughly as possible the interaction between the HFF and the TFS as well as the possible prolongation of the HFF into the TFS. West of the intersection between the transform fault (HFF) and the rift zone (TFS), the former splays with a gradual bending giving rise to a leading extensional imbricate fan. The westernmost structure of the rift, the N-S Gudfinnugja Fault (GF), is divided into two segments: the southern segment makes a junction with the HFF and is part of the imbricate fan; north of the junction instead, the northern GF appears right-laterally offset by about 20 m. Southeast of the junction, along the possible prolongation of the HFF across the TFS, the strike of the rift faults rotates in an anticlockwise direction, attaining a NNW-SSE orientation. Moreover, the TFS faults north of the HFF prolongation are fewer and have smaller offsets than those located to the south. Through the comparison between the structural data collected in the field at the HFF-TFS connection zone and a set of scaled experiments, we confirm a prolongation of the HFF through the rift, although here the transform fault has a much lower slip-rate than west of the junction. Our data suggest that transform fault terminations may be more complex than previously known, and propagate across a rift through a modification of the rift pattern.

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Section: Role Of Magma Intrusionssupporting

confidence: 48%

Interaction between Transform Faults and Rift Systems: A Combined Field and Experimental Approach

2016

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“…The Höfn site (r & 70 km), established as a permanent IGS (International GPS Service) station in 1997, serves as reference with an uplift rate of about 10 mm/a. A similar uplift rate was also observed independently by Á and by GEIRSSON et al (2006) for Höfn. At a station NW of Vatnajökull they found *20 mm/a uplift.…”

Section: Results For Rates Of Height and Gravity Changessupporting

confidence: 71%

“…The GPS points are listed in SJÖ BERG et al (2004). Additional GPS measurements were carried out, e.g., by Á and GEIRSSON et al (2006).…”

Section: Survey Region and Station Distributionmentioning

confidence: 99%

Temporal Gravity Variations near Shrinking Vatnajökull Ice Cap, Iceland

Jacoby

Hartmann

Wallner

et al. 2009

Pure appl. geophys.

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Repeated gravity measurements were carried out from 1991 until 1999 at sites SE of Vatnajökull, Iceland, to estimate the mass flow and deformation accompanying the shrinking of the ice cap. Published GPS data show an uplift of about 13 ± 5 mm/a near the ice margin. A gravity decrease of -2 ± 1 lGal/a relative to the Höfn base station, was observed for the same sites. Control measurements at the Höfn station showed a gravity decrease of -2 ± 0.5 lGal/a relative to the station RVIK 5473 at Reykjavík (about 250 km from Höfn). This is compatible, as a Bouguer effect, with a 10 ± 3 mm/a uplift rate of the IGS point at Höfn and an uplift rate of *20 mm/a near the ice margin. Although the derived gravity change rates at individual sites have large uncertainties, the ensemble of the rates varies systematically and significantly with distance from the ice. The relationship between gravity and elevation changes and the shrinking ice mass is modelled as response to the loading history. The GPS data can be explained by 1-D modelling (i.e., an earth model with a 15-km thick elastic lithosphere and a 7Á10 17 PaÁs asthenosphere viscosity), but not the gravity data. Based on 2-D modelling, the gravity data favour a low-viscosity plume in the form of a cylinder of 80 km radius and 10 17 to 10 18 PaÁs viscosity below a 6 km-thick elastic lid, embedded in a layered PREM-type earth, although the elevation data are less well explained by this model. Strain-porosity-hydrology effects are likely to enhance the magnitude of the gravity changes, but need verification by drilling. More accurate data may resolve the discrepancies or suggest improved models.

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“…1) on a tripod, drilled into the ice, ∼30 m upstream of the tephra layer boundary on 12 August 2013. A low-cost single frequency L1 receiver collected code and phase observations for 2 h each day and GPS reference station data of the ISGPS network (Geirsson and others, 2006) were used to calculate the differential tripod positions. This experiment lasted only for 33 d, because the set-up was damaged.…”

Section: Results From Field Datamentioning

confidence: 99%

Local surface mass-balance reconstruction from a tephra layer – a case study on the northern slope of Mýrdalsjökull, Iceland

Mayer¹,

Jaenicke

Lambrecht³

et al. 2016

J. Glaciol.

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ABSTRACT. Most Icelandic glaciers show high-accumulation rates during winter and strong surface melting during summer. Although it is difficult to establish and maintain mass-balance programs on these glaciers, mass-balance series do exist for several of the ice caps (Björnsson and others, 2013). We make use of the frequent volcanic eruptions in Iceland, which cause widespread internal tephra layers in the ice caps, to reconstruct the surface mass balance (SMB) in the ablation zone. This method requires information about surface geometry and ice velocity, derived from remote-sensing information. In addition, the emergence angle of the tephra layer needs to be known. As a proof-ofconcept, we utilize a prominent tephra layer of the Mýrdalsjökull Ice Cap to infer local SMB estimates in the ablation area back to 1988. Using tephra-layer outcrop locations across the glacier at different points in time it is possible to determine local mass changes (loss and redistribution) for a large part of the ablation zone, without the use of historic elevation models, which often are not available.

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Current plate movements across the Mid‐Atlantic Ridge determined from 5 years of continuous GPS measurements in Iceland

Cited by 85 publications

References 46 publications

Interaction between Transform Faults and Rift Systems: A Combined Field and Experimental Approach

Interaction between Transform Faults and Rift Systems: A Combined Field and Experimental Approach

Temporal Gravity Variations near Shrinking Vatnajökull Ice Cap, Iceland

Local surface mass-balance reconstruction from a tephra layer – a case study on the northern slope of Mýrdalsjökull, Iceland

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