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  • 51.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Palaeoseismology of glaciated terrain2015In: Encyclopedia of Earthquake Engineering / [ed] Beer, M., Kougioumtzoglou, I.A., Patelli, E., Au, I.S.-K., Berlin Heidelberg: Springer Berlin/Heidelberg, 2015Chapter in book (Refereed)
  • 52.
    Lund, Björn
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Geofysik.
    Stress variations during a glacial cycle at 500 m depth in Forsmark and Oskarshamn: Earth model effects2006Report (Other scientific)
  • 53.
    Lund, Björn
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Geophysics. geofysik.
    Bödvarsson, Reynir
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Geophysics. geofysik.
    Correlation of microearthquake body-wave spectral amplitudes2002In: Bulletin of the Seismological Society of America, Vol. 92, no 6, p. 2419-2433Article in journal (Refereed)
  • 54.
    Lund, Björn
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Geophysics. geofysik.
    Juhlin, Christopher
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Geophysics. geofysik.
    Comment on "Using borehole breakouts to constrain the complete stress tensor: Results from the Sijan Deep Drilling Project and offshore Santa Maria Basin, California" by Blair J. Zajac and Joann M. Stock2000In: Journal of Geophysical Research, Vol. 105, no B9, p. 21,847-21,849Article in journal (Refereed)
  • 55.
    Lund, Björn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Näslund, Jens-Ove
    Swedish Nuclear Fuel and Waste Management Co.
    Glacial isostatic adjustment: Implications for glacially induced faulting and nuclear waste repositories2009In: Volcanic and Tectonic Hazard Assessment for Nuclear Facilities / [ed] Connor, C.B., Chapman, N.A. and Connor, L.J, Cambridge University Press , 2009, p. 142-155Chapter in book (Other academic)
  • 56.
    Lund, Björn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Schmidt, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Hieronymus, Christoph
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Stress evolution and fault stability during the Weichselian glacial cycle2009Report (Other academic)
  • 57.
    Lund, Björn
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Geophysics. geofysik.
    Slunga, Ragnar
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Geophysics. geofysik.
    Stress tensor inversion using detailed microearthquake information and stability constraints: Application to Ölfus in southwest Iceland1999In: Journal of Geophysical Research, Vol. 104, no B7, p. 14,947-14,964Article in journal (Refereed)
  • 58.
    Lund, Björn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Slunga, Ragnar
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Bödvarsson, Reynir
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Estimates of current Icelandic stress tensors from the inversion of microearthquake fault plane solutions1996Conference paper (Refereed)
  • 59.
    Lund, Björn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Townend, J.
    Calculating horizontal stress orientations with full or partial knowledge of the tectonic stress tensor2007In: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 170, no 3, p. 1328-1335Article in journal (Refereed)
    Abstract [en]

    Earthquakes potentially serve as abundant and cost-effective gauges of tectonic stress provided that reliable means exist of extracting robust stress parameters. Several algorithms have been developed for this task, each of which typically provides information on the orientations of the three principal stresses and a single stress magnitude parameter. A convenient way of displaying tectonic stress results is to map the azimuth of maximum horizontal compressive stress, which is usually approximated using the azimuth of the larger subhorizontal principal stress. This approximation introduces avoidable errors that depend not only on the principal stress axes' plunges but also on the value of the stress magnitude parameter. Here we outline a method of computing the true direction of maximum horizontal compressive stress (SH) and show that this computation can be performed using only the four stress parameters obtained in routine focal mechanism stress estimation. Using theoretical examples and new stress inversion results obtained with focal mechanism data from the central Grímsey lineament, northern Iceland, we show that the SH axis may differ by tens of degrees from its commonly adopted proxy. In order to most appropriately compare tectonic stress estimates with other geophysical parameters, such as seismic fast directions or geodetically measured strain rate tensors, or to investigate spatiotemporal variations in stress, we recommend that full use be made of the routinely estimated stress parameters and that a formal axis of maximum horizontal compression be calculated.

  • 60.
    Lund, Björn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Townend, John
    Victoria University, Wellington, New Zeeland.
    Calculating horizontal stress orientations with full or partial knowledge of the tectonic stress tensor2007In: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 170, p. 1328-1335Article in journal (Refereed)
  • 61.
    Lund, Björn
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences, Geophysics. Geofysik.
    Zoback, Mark
    Orientation and magnitude of in situ stress to 6.5 km depth in the Baltic Shield1999In: International Journal of Rock Mechanics and Mining Sciences, Vol. 36, p. 169-190Article in journal (Refereed)
  • 62.
    Malehmir, Alireza
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Andersson, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Mehta, Suman
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Brodic, Bojan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Munier, Raymond
    Swedish Nucl Fuel & Waste Management Co SKB, Stockholm, Sweden..
    Place, Joachim
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Maries, Georgiana
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Smith, Colby
    Geol Survey Sweden, Uppsala, Sweden..
    Kamm, Jochen
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics. Univ Munster, Dept Geophys, D-48149 Munster, Germany..
    Bastani, Mehrdad
    Geol Survey Sweden, Uppsala, Sweden..
    Mikko, Henrik
    Geol Survey Sweden, Uppsala, Sweden..
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Post-glacial reactivation of the Bollnas fault, central Sweden: a multidisciplinary geophysical investigation2016In: Solid Earth, ISSN 1869-9510, E-ISSN 1869-9529, Vol. 7, no 2, p. 509-527Article in journal (Refereed)
    Abstract [en]

    Glacially induced intraplate faults are conspicuous in Fennoscandia where they reach trace lengths of up to 155 km with estimated magnitudes up to 8 for the associated earthquakes. While they are typically found in northern parts of Fennoscandia, there are a number of published accounts claiming their existence further south and even in northern central Europe. This study focuses on a prominent scarp discovered recently in lidar (light detection and ranging) imagery hypothesized to be from a post-glacial fault and located about 250 km north of Stockholm near the town of Bollnas. The Bollnas scarp strikes approximately north-south for about 12 km. The maximum vertical offset in the sediments across the scarp is 4-5m with the western block being elevated relative to the eastern block. To investigate potential displacement in the bedrock and identify structures in it that are related to the scarp, we conducted a multidisciplinary geophysical investigation that included gravity and magnetic measurements, high-resolution seismics, radio-magnetotellurics (RMT), electrical resistivity tomography (ERT) and ground-penetrating radar (GPR). Results of the investigations suggest a zone of low-velocity and high-conductivity in the bedrock associated with a magnetic lineament that is offset horizontally about 50m to the west of the scarp. The top of the bedrock is found similar to 10m below the surface on the eastern side of the scarp and about similar to 20m below on its western side. This difference is due to the different thicknesses of the overlying sediments accounting for the surface topography, while the bedrock surface is likely to be more or less at the same topographic level on both sides of the scarp; else the difference is not resolvable by the methods used. To explain the difference in the sediment covers, we suggest that the Bollnas scarp is associated with an earlier deformation zone, within a wide (> 150 m), highly fractured, water-bearing zone that became active as a reverse fault after the latest Weichselian deglaciation.

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  • 63.
    Mikko, Henrik
    et al.
    Sveriges geologiska undersökning.
    Smith, Colby
    Sveriges geologiska underökning.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Ask, Maria
    Luleå tekniska universitet.
    Munier, Raymond
    Svensk kärnbränslehantering AB.
    LiDAR-derived inventory of post-glacial fault scarps in Sweden2015In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 137, no 4, p. 334-338Article in journal (Refereed)
  • 64.
    Neytcheva, Maya
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis.
    Bängtsson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Numerical Analysis.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Numerical solution methods for glacial rebound models2004Report (Other academic)
  • 65.
    Pagli, Carolina
    et al.
    University of Iceland.
    Sigmundsson, Freysteinn
    University of Iceland.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Sturkell, Erik
    Göteborgs universitet.
    Geirsson, Halldor
    Icelandic Meteorological Office.
    Einarsson, Páll
    University of Iceland.
    Árnadóttir, Thóra
    University of Iceland.
    Sigrun, Hreinsdottir
    University of Iceland.
    Glacio-isostatic deformation around the Vatnajökull ice cap, Iceland, induced by recent climate warming: GPS observations and finite element modeling2007In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 112, no B8, p. B08405-Article in journal (Refereed)
    Abstract [en]

    [1] Glaciers in Iceland began retreating around 1890, and since then the Vatnajokull ice cap has lost over 400 km 3 of ice. The associated unloading of the crust induces a glacio-isostatic response. From 1996 to 2004 a GPS network was measured around the southern edge of Vatnajokull. These measurements, together with more extended time series at several other GPS sites, indicate vertical velocities around the ice cap ranging from 9 to 25 mm/yr, and horizontal velocities in the range 3 to 4 mm/yr. The vertical velocities have been modeled using the finite element method (FEM) in order to constrain the viscosity structure beneath Vatnajokull. We use an axisymmetric Earth model with an elastic plate over a uniform viscoelastic half-space. The observations are consistent with predictions based on an Earth model made up of an elastic plate with a thickness of 10-20 km and an underlying viscosity in the range 4-10 x 10(18) Pa s. Knowledge of the Earth structure allows us to predict uplift around Vatnajokull in the next decades. According to our estimates of the rheological parameters, and assuming that ice thinning will continue at a similar rate during this century (about 4 km 3/year), a minimum uplift of 2.5 meters between 2000 to 2100 is expected near the current ice cap edge. If the thinning rates were to double in response to global warming (about 8 km 3/year), then the minimum uplift between 2000 to 2100 near the current ice cap edge is expected to be 3.7 meters.

  • 66.
    Poutanen, Markku
    et al.
    Finnish Geodetic Institute.
    Dransch, Doris
    GeoForschungsZentrum Potsdam.
    Gregersen, Sören
    GEUS Copenhagen.
    Haubrock, Sören
    GeoForschungsZentrum Potsdam.
    Ivins, Eric
    Jet Propulsion Laboratory.
    Klemann, Volker
    GeoForschungsZentrum Potsdam.
    Kozlovskaya, Elena
    University of Oulu.
    Kukkonen, Ilmo
    Geological Survey of Finland.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Lunkka, Juha-Pekka
    University of Oulu.
    Milne, Glenn
    University of Ottawa.
    Müller, Jürgen
    University of Hannover.
    Pascal, Christophe
    Geological Survey of Norway.
    Pettersen, Bjørn
    Norwegian University of Life Science.
    Scherneck, Hans-Georg
    Chalmers University of Technology.
    Steffen, Holger
    University of Calgary.
    Vermeersen, Bert
    DEOS, TU Delft.
    Wolf, Detlef
    GeoForschungsZentrum Potsdam.
    DynaQlim – Upper Mantle Dynamics and Quaternary Climate in Cratonic Areas2010In: New Frontiers in Integrated Solid Earth Sciences / [ed] S. Cloetingh, J. Negendank, Springer, 2010, p. 349-372Chapter in book (Other academic)
    Abstract [en]

    The isostatic adjustment of the solid Earth to the glacial loading (GIA, Glacial Isostatic Adjustment) with its temporal signature offers a great opportunity to retrieve information of Earth’s upper mantle to the changing mass of glaciers and ice sheets, which in turn is driven by variations in Quaternary climate. DynaQlim (Upper Mantle Dynamics and Quaternary Climate in Cratonic Areas) has its focus to study the relations between upper mantle dynamics, its composition and physical properties, temperature, rheology, and Quaternary climate. Its regional focus lies on the cratonic areas of northern Canada and Scandinavia.

    Geodetic methods like repeated precise levelling, tide gauges, high-resolution observations of recent movements, gravity change and monitoring of postglacial faults have given information on the GIA process for more than 100 years. They are accompanied by more recent techniques like GPS observations and the GRACE and GOCE satellite missions which provide additional global and regional constraints on the gravity field. Combining geodetic observations with seismological investigations, studies of the postglacial faults and continuum mechanical modelling of GIA, DynaQlim offers new insights into properties of the lithosphere. Another step toward a better understanding of GIA has been the joint inversion of different types of observational data – preferentially connected with geological relative sea-level evidence of the Earth’s rebound during the last 10,000 years.

    Due to the changes in the lithospheric stress state large faults ruptured violently at the end of the last glaciation in large earthquakes, up to the magnitudes MW = 7–8. Whether the rebound stress is still able to trigger a significant fraction of intraplate seismic events in these regions is not completely understood due to the complexity and spatial heterogeneity of the regional stress field. Understanding of this mechanism is of societal importance.

    Glacial ice sheet dynamics are constrained by the coupled process of the deformation of the viscoelastic solid Earth, the ocean and climate variability. Exactly how the climate and oceans reorganize to sustain growth of ice sheets that ground to continents and shallow continental shelves is poorly understood. Incorporation of nonlinear feedback in modelling both ocean heat transport systems and atmospheric CO2 is a major challenge. Climate-related loading cycles and episodes are expected to be important, hence also more short-term features of palaeoclimate should be explicitly treated.

    Within this Chapter View Chapter

    1. Introduction
    2. Observational Basis
    3. Current Models and Problems to be Solved
    4. Climate
    5. Challenges with DynaQlim
    6. References
    7. References

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  • 67.
    Reynir, Bödvarsson
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Geofysik.
    Björn, Lund
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Geofysik.
    Roland, Roberts
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Geofysik.
    Ragnar, Slunga
    Earthquake activity in Sweden. Study in connection with a proposed nuclear waste repository in Forsmark or Oskarshamn2006Report (Other scientific)
  • 68.
    Reynir, Bödvarsson
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Geofysik.
    Björn, Lund
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Earth Sciences, Department of Earth Sciences. Geofysik.
    Roland, Roberts
    Ragnar, Slunga
    Ari, Tryggvason
    Seismologisk studie relaterad till Citybanan i Stockholm2004Report (Other scientific)
  • 69.
    Schmidt, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Hieronymus, Christoph
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Implementation of the glacial rebound pre-stress advection correction in general-purpose finite element analysis software: Springs versus foundations2012In: Computers & Geosciences, ISSN 0098-3004, E-ISSN 1873-7803, Vol. 40, p. 97-106Article in journal (Refereed)
    Abstract [en]

    When general-purpose finite element analysis software is used to model glacial isostatic adjustment (GIA), the first-order effect of prestress advection has to be accounted for by the user. We show here that the common use of elastic foundations at boundaries between materials of different densities will produce incorrect displacements, unless the boundary is perpendicular to the direction of gravity. This is due to the foundations always acting perpendicular to the surface to which they are attached, while the body force they represent always acts in the direction of gravity. If prestress advection is instead accounted for by the use of elastic spring elements in the direction of gravity, the representation will be correct. The use of springs adds a computation of the spring constants to the analysis. The spring constant for a particular node is defined by the product of the density contrast at the boundary, the gravitational acceleration, and the area supported by the node. To be consistent with the finite element formulation, the area is evaluated by integration of the nodal shape functions. We outline an algorithm for the calculation and include a Python script that integrates the shape functions over a bilinear quadrilateral element. For linear rectangular and triangular elements, the area supported by each node is equal to the element area divided the number of defining nodes, thereby simplifying the computation. This is, however, not true in the general nonrectangular case, and we demonstrate this with a simple 1-element model. The spring constant calculation is simple and performed in the preprocessing stage of the analysis. The time spent on the calculation is more than compensated for by a shorter analysis time, compared to that for a model with foundations. We illustrate the effects of using springs versus foundations with a simple two-dimensional GIA model of glacial loading, where the Earth model has an inclined boundary between the overlying elastic layer and the lower viscoelastic layer. Our example shows that the error introduced by the use of foundations is large enough to affect an analysis based on high-accuracy geodetic data.

  • 70.
    Schmidt, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Hieronymus, Christoph
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Maclennan, John
    Department of Earth Sciences, University of Cambridge.
    Árnadóttir, Thora
    Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland.
    Pagli, Carolina
    School of Earth and Environment, University of Leeds.
    Effects of present day deglaciation on melt production rates beneath Iceland2013In: Journal of Geophysical Research-Solid Earth, ISSN 2169-9313, Vol. 118, no 7, p. 3366-3379Article in journal (Other academic)
    Abstract [en]

    Ongoing deglaciation in Iceland not only causes uplift at the surface but also increases magma production at depth due to decompression of the mantle. Here we study glacially induced decompression melting using 3-D models of glacial isostatic adjustment in Iceland since 1890. We find that the mean glacially induced pressure rate of change in the mantle increases melt production rates by 100–135%, or an additional 0.21–0.23 km3 of magma per year beneath Iceland. Approximately 50% of this melt is produced underneath central Iceland. The greatest volumetric increase is found directly beneath Iceland's largest ice cap, Vatnajökull, colocated with the most productive volcanoes. Our models of the effect of deglaciation on mantle melting predict a significantly larger volumetric response than previous models which only considered the effect of deglaciation of Vatnajökull, and only mantle melting directly below Vatnajökull. Although the ongoing deglaciation significantly increases the melt production rate, the increase in melt supply rate at the base of the lithosphere is delayed and depends on the melt ascent velocity through the mantle. Assuming that 25% of the melt reaches the surface, the upper limit on our deglaciation-induced melt estimates for central Iceland would be equivalent to an eruption the size of the 2010 Eyjafjallajökull summit eruption every seventh year.

  • 71.
    Schmidt, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Näslund, Jens-Ove
    Swedish Nuclear Fuel and Waste Management Organization.
    Fastook, James
    University of Maine.
    Comparing a thermo-mechanical Weichselian Ice Sheet reconstruction to reconstructions based on the sea level equation: aspects of ice configurations and glacial isostatic adjustment2014In: Solid Earth, ISSN 1869-9510, E-ISSN 1869-9529, Vol. 5, no 1, p. 371-388Article in journal (Refereed)
    Abstract [en]

    In this study we compare a recent reconstruction of the Weichselian Ice Sheet as simulated by the University of Maine ice sheet model (UMISM) to two reconstructions commonly used in glacial isostatic adjustment (GIA) modelling: ICE-5G and ANU (Australian National University, also known as RSES). The UMISM reconstruction is carried out on a regional scale based on thermo-mechanical modelling, whereas ANU and ICE-5G are global models based on the sea level equation. The three models of the Weichselian Ice Sheet are compared directly in terms of ice volume, extent and thickness, as well as in terms of predicted glacial isostatic adjustment in Fennoscandia. The three reconstructions display significant differences. Whereas UMISM and ANU includes phases of pronounced advance and retreat prior to the last glacial maximum (LGM), the thickness and areal extent of the ICE-5G ice sheet is more or less constant up until the LGM. During the post-LGM deglaciation phase ANU and ICE-5G melt relatively uniformly over the entire ice sheet in contrast to UMISM, which melts preferentially from the edges, thus reflecting the fundamental difference in the reconstruction scheme. We find that all three reconstructions fit the present-day uplift rates over Fennoscandia equally well, albeit with different optimal earth model parameters. Given identical earth models, ICE-5G predicts the fastest present-day uplift rates, and ANU the slowest. Moreover, only for ANU can a unique best-fit model be determined. For UMISM and ICE-5G there is a range of earth models that can reproduce the present-day uplift rates equally well. This is understood from the higher present-day uplift rates predicted by ICE-5G and UMISM, which result in bifurcations in the best-fit upper-and lower-mantle viscosities. We study the areal distributions of present-day residual surface velocities in Fennoscandia and show that all three reconstructions generally over-predict velocities in southwestern Fennoscandia and that there are large differences in the fit to the observational data in Finland and northernmost Sweden and Norway. These difference may provide input to further enhancements of the ice sheet reconstructions.

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  • 72.
    Schmidt, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Árnadóttir, Thora
    Nordic Volcanological Center, Institute of Earth Sciences, University of Iceland, Reykjavík, Iceland.
    Schmeling, Harro
    Institute of Earth Sciences, Section Geophysics, J. W. Goethe-University, Frankfurt am Main, Germany.
    Glacial isostatic adjustment constrains dehydration stiffening beneath Iceland2012In: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 359-360, p. 152-161Article in journal (Refereed)
    Abstract [en]

    During melting in the upper mantle the preferred partitioning of water into the melt will effectively dehydrate the solid residue. Linear extrapolation of laboratory experiments suggests that dehydration can produce a sharp viscosity contrast (increase) of a factor 500 across the dry solidus. In this study we show that the suggested magnitude of dehydration stiffening in a plume–ridge setting is incompatible with the present glacial isostatic adjustment (GIA) in Iceland. Using GPS observations of current GIA in Iceland, we find that the data are best fit by a viscosity contrast over the dry solidus in the range 0.5–3. A viscosity contrast higher than 10 requires a mantle viscosity below the dry solidus lower than , depending on the thickness of the dehydrated layer. A viscosity contrast of 100 or more demands a mantle viscosity of or less. However, we show here that a non-linear extrapolation of the laboratory data predicts a viscosity contrast as low as a factor 3–29, assuming conditions of constant strain rate to constant viscous dissipation rate. This is compatible with our GIA results and suggests that the plume–ridge interaction beneath Iceland is governed by a non-linear rheology and controlled by a combination of kinematic and dynamic boundary conditions rather than buoyant forces alone.

  • 73.
    Sgattoni, Giulia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics. Univ Bologna, Dept Biol Geol & Environm Sci, Bologna, Italy; Univ Iceland, Inst Sci, Inst Earth Sci, Reykjavik, Iceland.
    Jeddi, Zeinab
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Gudmundsson, Ólafur
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Einarsson, Pall
    Univ Iceland, Inst Sci, Inst Earth Sci, Reykjavik, Iceland.
    Tryggavson, Ari
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Lucchi, Federico
    Univ Bologna, Dept Biol Geol & Environm Sci, Bologna, Italy.
    Long-period seismic events with strikingly regular temporal patterns on Katla volcano’s south flank (Iceland)2016In: Journal of Volcanology and Geothermal Research, ISSN 0377-0273, E-ISSN 1872-6097, Vol. 324, p. 28-40Article in journal (Refereed)
    Abstract [en]

    Katla is a threatening volcano in Iceland, partly covered by the Myrdalsjokull ice cap. The volcano has a large caldera with several active geothermal areas. A peculiar cluster of long-period seismic events started on Katla's south flank in July 2011, during an unrest episode in the caldera that culminated in a glacier outburst. The seismic events were tightly clustered at shallow depth in the Gvendarfell area, 4 km south of the caldera, under a small glacier stream at the southern margin of Myrdalsjokull. No seismic events were known to have occurred in this area before. The most striking feature of this seismic cluster is its temporal pattern, characterized by regular intervals between repeating seismic events, modulated by a seasonal variation. Remarkable is also the stability of both the time and waveform features over a long time period, around 3.5 years. We have not found any comparable examples in the literature. Both volcanic and glacial processes can produce similar waveforms and therefore have to be considered as potential seismic sources. Discerning between these two causes is critical for monitoring glacier-clad volcanoes and has been controversial at Katla. For this new seismic cluster on the south flank, we regard volcano-related processes as more likely than glacial ones for the following reasons: 1) the seismic activity started during an unrest episode involving sudden melting of the glacier and a jokulhlaup; 2) the glacier stream is small and stagnant; 3) the seismicity remains regular and stable for years; 4) there is no apparent correlation with short-term weather changes, such as rainstorms. We suggest that a small, shallow hydrothermal system was activated on Katla's south flank in 2011, either by a minor magmatic injection or by changes of permeability in a local crack system.

  • 74.
    Sigmundsson, Freysteinn
    et al.
    University of Iceland.
    Albino, Fabien
    University of Iceland.
    Schmidt, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Pinel, Virginie
    Université de Savoie.
    Hooper, Andrew
    Delft University of Technology.
    Pagli, Carolina
    University of Leeds.
    Multiple effects of ice load changes and associated stress change on magmatic systems2013In: Climate Forcing of Geological and Geomorphological Hazards / [ed] W.J. McGuire, M.A. Maslin, John Wiley & Sons, 2013Chapter in book (Refereed)
  • 75. Sigmundsson, Freysteinn
    et al.
    Pinel, Virginie
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Albino, Fabien
    Pagli, Carolina
    Geirsson, Halldór
    Sturkell, Erik
    Climate effects on volcanism: influence on magmatic systems of loading and unloading from ice mass variations, with examples from Iceland2010In: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 368, no 1919, p. 2519-2534Article in journal (Refereed)
    Abstract [en]

    Pressure influences both magma production and the failure of magma chambers. Changes in pressure interact with the local tectonic settings and can affect magmatic activity. Present-day reduction in ice load on subglacial volcanoes due to global warming is modifying pressure conditions in magmatic systems. The large pulse in volcanic production at the end of the last glaciation in Iceland suggests a link between unloading and volcanism, and models of that process can help to evaluate future scenarios. A viscoelastic model of glacio-isostatic adjustment that considers melt generation demonstrates how surface unloading may lead to a pulse in magmatic activity. Iceland's ice caps have been thinning since 1890 and glacial rebound at rates exceeding 20 mm yr(-1) is ongoing. Modelling predicts a significant amount of 'additional' magma generation under Iceland due to ice retreat. The unloading also influences stress conditions in shallow magma chambers, modifying their failure conditions in a manner that depends critically on ice retreat, the shape and depth of magma chambers as well as the compressibility of the magma. An annual cycle of land elevation in Iceland, due to seasonal variation of ice mass, indicates an annual modulation of failure conditions in subglacial magma chambers.

  • 76. Spada, G.
    et al.
    Barletta, V. R.
    Klemann, V.
    Riva, R. E. M.
    Martinec, Z.
    Gasperini, P.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Wolf, D.
    Vermeersen, L. L. A.
    King, M. A.
    A benchmark study for glacial isostatic adjustment codes2011In: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 185, no 1, p. 106-132Article in journal (Refereed)
    Abstract [en]

    The study of glacial isostatic adjustment (GIA) is gaining an increasingly important role within the geophysical community. Understanding the response of the Earth to loading is crucial in various contexts, ranging from the interpretation of modern satellite geodetic measurements (e. g. GRACE and GOCE) to the projections of future sea level trends in response to climate change. Modern modelling approaches to GIA are based on various techniques that range from purely analytical formulations to fully numerical methods. Despite various teams independently investigating GIA, we do not have a suitably large set of agreed numerical results through which the methods may be validated; a community benchmark data set would clearly be valuable. Following the example of the mantle convection community, here we present, for the first time, the results of a benchmark study of codes designed to model GIA. This has taken place within a collaboration facilitated through European Cooperation in Science and Technology (COST) Action ES0701. The approaches benchmarked are based on significantly different codes and different techniques. The test computations are based on models with spherical symmetry and Maxwell rheology and include inputs from different methods and solution techniques: viscoelastic normal modes, spectral-finite elements and finite elements. The tests involve the loading and tidal Love numbers and their relaxation spectra, the deformation and gravity variations driven by surface loads characterized by simple geometry and time history and the rotational fluctuations in response to glacial unloading. In spite of the significant differences in the numerical methods employed, the test computations show a satisfactory agreement between the results provided by the participants.

  • 77.
    Steffen, Rebekka
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Audet, Pascal
    Univ Ottawa, Dept Earth & Environm Sci, Ottawa, ON, Canada.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Weakened Lithosphere Beneath Greenland Inferred From Effective Elastic Thickness: A Hot Spot Effect?2018In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 45, no 10, p. 4733-4742Article in journal (Refereed)
    Abstract [en]

    The effective elastic thickness (T-e) of the lithosphere provides geophysical information about long-term flexural strength and can be used to constrain thermorheological properties of the lithosphere. T-e is typically calculated from the spectral analysis of gravity and topography data; variations in T-e are, however, not well resolved in Greenland due to poor constraints on crustal structure (including crustal thickness) and complications due to ice loading. In addition, geological and geophysical constraints on the tectonic history of Greenland are sparse due to the thick ice cover. Here we use the global gravity model EIGEN-6C4 together with a new model of the crust-mantle boundary to obtain a high-resolution T-e map of Greenland. The distribution of T-e indicates reduced strength in the lower crust and lithospheric mantle beneath southern and central Greenland, which may be due to the passage of the Iceland hot spot during the last 100Ma. In contrast, the northern part of Greenland shows a large T-e, implying mechanical coupling between crust and uppermost mantle and suggesting the existence of a cold and strong tectonic unit. In a relative sense, the distribution of T-e values is consistent with estimates of lithospheric thickness based on seismic velocity models, indicating a dominantly thermal control on lithospheric structure and evolution.

    Plain Language Summary Greenland is covered by a large ice sheet; its geodynamic history is therefore mostly unknown as only the coastal areas are accessible for direct geological sampling. However, geophysical data can be used to investigate the lithospheric structure to infer its geodynamic history. Here we use satellite gravity data together with elevation data and a crustal density model to look at the distribution of the effective elastic thickness, which provides information about the variations in strength of the lithosphere. We find that most of Greenland's lithosphere is weaker than expected given its age of formation (approximate to 1 billion years), suggesting that it was affected by a thermal event within the last approximate to 400 million years. We interpret the weakness in the lithosphere as a result of the movement of Greenland with respect to hot mantle material, which is now located beneath Iceland leading to large volcanism there. The results of this study show for the first time the effect of the hot mantle material on the lithosphere of Greenland, which can help us identify the different possible tracks of the moving hot mantle material and understand the stability of the ice sheet.

  • 78.
    Steffen, Rebekka
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Strykowski, Gabriel
    Tech Univ Denmark, Natl Space Inst, Geodynam, Bldg 328, DK-2800 Lyngby, Denmark..
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    High-resolution Moho model for Greenland from EIGEN-6C4 gravity data2017In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 706/707, p. 206-220Article in journal (Refereed)
    Abstract [en]

    The crust-mantle boundary (the Moho) is a first order interface in the Earth and the depth to the Moho is therefore well studied in most regions. However, below regions which are covered by large ice sheets, such as Greenland and Antarctica, the Moho is only partly known and seismic data are difficult to obtain. Here, we take advantage of the global gravity model EIGEN-6C4, together with the Parker-Oldenburg algorithm, to estimate the depth to the Moho beneath Greenland and surroundings. The available free-air gravity data are corrected for the topographic effect and the effect of sedimentary basins. We also correct for the effect on gravity due to the weight of the ice sheet and the accompanying deflection of the Earth's surface, which has not previously been taken into account in gravity studies of currently glaciated regions. Our final Moho depth model for Greenland has an associated uncertainty of +/- 4.5 km for areas with sedimentary basins and 4 km for areas without sedimentary basins. The model shows maximum Moho depths below east Greenland of up to 55 km and values less than 20 km offshore east Greenland. There is a marked increase in Moho depth of 10-15 km from northern to central Greenland, indicating a significant change in geology. A deep Moho at the northern coast of Greenland towards Ellesmere Island might be related to the location of the hot-spot track. Our Moho model is consistent with previous models, but has a higher lateral resolution of 0.1 degrees and covers the entire area of on- and offshore Greenland.

  • 79.
    Steffen, Rebekka
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Wu, Patrick
    University of Hong Kong.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Fault activation dueto glacially induced stresses2013Conference paper (Refereed)
  • 80.
    Tarvainen, Matti
    et al.
    Helsinki University.
    Valtonen, Outi
    Helsinki University.
    Husebye, Eystein
    BCCS, Uni Research Bergen.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Seismic analysis of aircraft accidents2013In: Natural Science, ISSN 2150-4091, E-ISSN 2150-4105, Vol. 5, no 7, p. 811-817Article in journal (Refereed)
    Abstract [en]

    Seismic records from Finnish and Swedish sta- tions were analyzed for a study of two aircraft accidents in Finland and Sweden. A Hornet F-18 fighter crashed in central Finland, and analysis of recorded impact signals from 7 nearby seis- mic stations yielded in a crash location only 4 km in error. An estimated magnitude (ML) of 0.5 units gave an impact velocity of 335 m/sec (1200 km/h), which was in excellent agreement with that reported by the Finnish Air Force. A Norwegian Hercules transport plane crashed in foul weather near the summit of Mt. Kebnekaise, NW Sweden. Both seismic and infrasound signals were weak, and in our interpretation, this implied that the Hercules aircraft had a less steep impact angle against the mountain. We also examined seismic analyses of other spectacular air accidents like that of Lockerbie, UK in 1988, and terrorist air- craft attacks on September 11th, 2001 in the USA. Likewise, accidents at sea, such as the sinking of the Russian submarine Kursk in the Barents sea in 2000, and the freighter M/S Rocknes near Bergen in 2004, were recorded and analyzed seismically. In this study, we demonstrated that it was feasible to use seismic registrations to locate impact sites, and to define the exact time of such accidents. Also, negative evidence, i.e., lack of seismic recordings, may provide some information of such accidents and their conse-quences.

  • 81.
    Wagner, Frederic
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Tryggvason, Ari
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Roberts, Roland G.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Gudmundsson, Ólafur
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Automatic seismic event detection using migration and stacking: a performance and parameter study in Hengill, southwest Iceland2017In: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 209, no 3, p. 1866-1877Article in journal (Refereed)
    Abstract [en]

    We investigate the performance of a seismic event detection algorithm using migration and stacking of seismic traces. The focus lies on determining optimal data dependent detection parameters for a data set from a temporary network in the volcanically active Hengill area, southwest Iceland. We test variations of the short-term average to long-term average and Kurtosis functions, calculated from filtered seismic traces, as input data. With optimal detection parameters, our algorithm identified 94 per cent (219 events) of the events detected by the South Iceland Lowlands (SIL) system, that is, the automatic system routinely used on Iceland, as well as a further 209 events, previously missed. The assessed number of incorrect (false) detections was 25 per cent for our algorithm, which was considerably better than that from SIL (40 per cent). Empirical tests show that well-functioning processing parameters can be effectively selected based on analysis of small, representative subsections of data. Our migration approach is more computationally expensive than some alternatives, but not prohibitively so, and it appears well suited to analysis of large swarms of low magnitude events with interevent times on the order of seconds. It is, therefore, an attractive, practical tool for monitoring of natural or anthropogenic seismicity related to, for example, volcanoes, drilling or fluid injection.

  • 82.
    Zardari, Muhammad Auchar
    et al.
    Quaid E Awam Univ Engn Sci & Technol, Dept Civil Engn, Nawabshah, Sindh, Pakistan..
    Mattsson, Hans
    Lulea Univ Technol, Dept Civil Environm & Nat Resources Engn, S-97187 Lulea, Sweden..
    Knutsson, Sven
    Lulea Univ Technol, Dept Civil Environm & Nat Resources Engn, S-97187 Lulea, Sweden..
    Khalid, Muhammad Shehzad
    Kyoto Univ, Dept Urban Management, Kyoto, Japan..
    Ask, Maria V. S.
    Lulea Univ Technol, Dept Civil Environm & Nat Resources Engn, S-97187 Lulea, Sweden..
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Numerical Analyses of Earthquake Induced Liquefaction and Deformation Behaviour of an Upstream Tailings Dam2017In: Advances in Materials Science and Engineering, ISSN 1687-8434, E-ISSN 1687-8442, article id 5389308Article in journal (Refereed)
    Abstract [en]

    Much of the seismic activity of northern Sweden consists of micro-earthquakes occurring near postglacial faults. However, larger magnitude earthquakes do occur in Sweden, and earthquake statistics indicate that a magnitude 5 event is likely to occur once every century. This paper presents dynamic analyses of the effects of larger earthquakes on an upstream tailings dam at the Aitik copper mine in northern Sweden. The analyses were performed to evaluate the potential for liquefaction and to assess stability of the dam under two specific earthquakes: a commonly occurring magnitude 3.6 event and a more extreme earthquake of magnitude 5.8. The dynamic analyses were carried out with the finite element program PLAXIS using a recently implemented constitutive model called UBCSAND. The results indicate that the magnitude 5.8 earthquake would likely induce liquefaction in a limited zone located below the ground surface near the embankment dikes. It is interpreted that stability of the dam may not be affected due to the limited extent of the liquefied zone. Both types of earthquakes are predicted to induce tolerable magnitudes of displacements. The results of the postseismic slope stability analysis, performed for a state after a seismic event, suggest that the dam is stable during both the earthquakes.

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  • 83.
    Árnadóttir, Thóra
    et al.
    University of Iceland.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Jiang, Wei
    Wuhan University.
    Geirsson, Halldor
    Icelandic Meteorological Office.
    Björnsson, Helgi
    University of Iceland.
    Einarsson, Páll
    University of Iceland.
    Sigurdsson, T
    National Land Survey of Iceland.
    Glacial rebound and plate spreading: results from the first countrywide GPS observations in Iceland2009In: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 177, no 2, p. 691-716Article, review/survey (Refereed)
    Abstract [en]

    Iceland is one of the few places on Earth where a divergent plate boundary can be observed on land. Direct observations of crustal deformation for the whole country are available for the first time from nationwide Global Positioning System (GPS) campaigns in 1993 and 2004. The plate spreading across the island is imaged by the horizontal velocity field and high uplift rates (>= 10 mm yr(-1)) are observed over a large part of central and southeastern Iceland. Several earthquakes, volcanic intrusions and eruptions occurred during the time spanned by the measurements, causing local disturbances of the deformation field. After correcting for the largest earthquakes during the observation period, we calculate the strain rate field and find that the main feature of the field is the extension across the rift zones, subparallel to the direction of plate motion. Kinematic models of the horizontal plate spreading signal indicate a slightly elevated rate of spreading in the Northern Volcanic Zone (NVZ) (23 +/- 2 mm yr(-1)), while the rates at the other plate boundary segments agree fairly well with the predicted rate of plate spreading (similar to 20 mm yr(-1)) across Iceland. The horizontal ISNET velocities across north Iceland therefore indicate that the excessive spreading rate (>30 mm yr(-1)) observed by GPS in 1987-1992 following the 1975-1984 Krafla rifting episode was significantly slower during 1993-2004. We model the vertical velocities using glacial isostatic adjustment (GIA) due to the recent thinning of the largest glaciers in Iceland. A layered earth model with a 10-km thick elastic layer, underlain by a 30-km thick viscoelastic layer with viscosity 1 x 10(20) Pa s, over a half-space with viscosity similar to 1 x 10(19) Pa s can explain the broad area of uplift in central and southeastern Iceland. A wide area of significant residual uplift ( up to 8 mm yr(-1)) is evident in north Iceland after we subtract the rebound signal from the observed rates, whereas the Reykjanes Peninsula and the Western Volcanic Zone (WVZ) appear to be subsiding at a rate of 4-8 mm yr(-1). We observe a coherent pattern of small but significant residual horizontal motion (up to 3 mm yr(-1)) away from Vatnajokull and the smaller glaciers that is most likely caused by glacial rebound. Our study demonstrates that the velocity field over a large part of Iceland is affected by deglaciation and that this effect needs to be considered when interpreting deformation data to monitor subglacial volcanoes in Iceland.

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