| 1. |
- Geirsson, H., et al.
(författare)
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Overview of results from continuous GPS observations in Iceland from 1995 to 2010
- 2010
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Ingår i: Jökull. - 0449-0576. ; 60:1, s. 1-21
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Tidskriftsartikel (refereegranskat)abstract
- Iceland is a natural laboratory for a variety of processes associated with crustal deformation, such as earthquakes, magmatic events, tectonic plate motions, and glacial load changes. Continuous GPS (CGPS) measurements started in Iceland in 1995, and since then data from the network have helped to shed light on many different active deformation processes. The number of CGPS sites in Iceland tripled during 2006–2008, as a result of an international collaborative effort coordinated by Icelandic scientists. By early 2010 the number of CGPS stations in Iceland had reached 64, located primarily around and within the North- American–Eurasian plate boundary zone. Since its initiation, the CGPS network has played an important role in monitoring volcanoes and seismogenic areas, most notably during the 2009–2010 Eyjafjallajökull volcano unrest. Plate spreading of up to 2 cm per year usually dominates the horizontal motion observed at the CGPS sites, while uplift is observed at many of the stations due to recent retreat of the Icelandic ice caps. Co-seismic and post-seismic deformation of the largest earthquakes in 2000 and 2008 in the South Iceland Seismic Zone were captured by the network, and high-rate (1 Hz) CGPS observations helped to identify two magnitude 6 mainshocks in 2008 that were separated in time by only 2–3 seconds. The CGPS network has thus enabled us to monitor deformation occurring over days to months caused by migration of magma or fluids, post-seismic transients, rapid deformation caused by earthquakes and eruptions, as well as the long term plate spreading signal.
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| 2. |
- Sigmundsson, F., et al.
(författare)
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Intrusion triggering of the 2010 Eyjafjallajökull explosive eruption
- 2010
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Ingår i: Nature. ; 468:7322, s. 426-430
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Tidskriftsartikel (refereegranskat)abstract
- Gradual inflation of magma chambers often precedes eruptions at highly active volcanoes. During such eruptions, rapid deflation occurs as magma flows out and pressure is reduced1–3. Less is known about the deformation style at moderately active volcanoes, such as Eyjafjallajo¨kull, Iceland, where an explosive summit eruption of trachyandesite beginning on 14 April 2010 caused exceptional disruption to air traffic, closing airspace over much of Europe for days. This eruption was preceded by an effusive flank eruption of basalt from 20 March to 12 April 2010. The 2010 eruptions are the culmination of 18 years of intermittent volcanic unrest4–9. Here we show that deformation associated with the eruptions was unusual because it did not relate to pressure changes within a single magma chamber. Deformation was rapid before the first eruption (.5mm per day after 4 March), but negligible during it. Lack of distinct co-eruptive deflation indicates that the net volume of magma drained from shallow depth during this eruption was small; rather, magma flowed from considerable depth. Before the eruption, a 0.05km3 magmatic intrusion grew over a period of three months, in a temporally and spatially complex manner, as revealed by GPS (Global Positioning System) geodetic measurements and interferometric analysis of satellite radar images. The second eruption occurred within the ice-capped caldera of the volcano, with explosivity amplified by magma–ice interaction. Gradual contraction of a source, distinct from the pre-eruptive inflation sources, is evident from geodetic data. Eyjafjallajo¨kull’s behaviour can be attributed to its off-rift setting with a ‘cold’ subsurface structure and limited magma at shallow depth, as may be typical for moderately active volcanoes. Clear signs of volcanic unrest signals over years to weeks may indicate reawakening of such volcanoes, whereas immediate short-term eruption precursors may be subtle and difficult to detect.
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| 3. |
- Hreinsdottir, S, et al.
(författare)
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A complex earthquake sequence captured by the continuous GPS network in SW Iceland
- 2009
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 36:12, s. L12309-
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Tidskriftsartikel (refereegranskat)abstract
- A complex sequence of earthquakes struck the western part of the South Iceland Seismic Zone (SISZ) on 29 May 2008. The sequence initiated with a M(w)6.3 (NEIC) earthquake in the western part of the SISZ. Aftershocks from the earthquake delineate two parallel N-S trending structures 4 km apart, in addition to activity along an E-W zone further westward. Continuous GPS measurements can best be explained by right-lateral strike-slip motion on two parallel N-S trending faults, with little slip occurring on other structures illuminated by earthquake activity. We estimate a total moment release of M(w)6.2, with M(w)6.1 on the first rupture and M(w)6.0 on the second rupture. High rate (1 Hz) CGPS data from a near-field station suggest that the main asperity on the Kross fault ruptured within 3 s of the initial mainshock on the Ingolfsfjall fault. Citation: Hreinsdottir, S., T. Amadottir, J. Decriem, H. Geirsson, A. Tryggvason, R. A. Bennett, and P. LaFemina (2009), A complex earthquake sequence captured by the continuous GPS network in SW Iceland, Geophys. Res. Lett., 36, L12309, doi: 10.1029/2009GL038391.
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