HR: 0800h
AN: G51B-0076    [Abstracts]
TI: Crustal Deformation in Iceland: Constraints on Tectonic and Magmatic Processes from InSAR observations
AU: Pedersen, R
EM: rikke@hi.is
AF: Institue of Earth Sciences, University of Iceland, Reykjavik, IS-101 Iceland
AU: * Sigmundsson, F
EM: fs@hi.is
AF: Institue of Earth Sciences, University of Iceland, Reykjavik, IS-101 Iceland
AU: Feigl, K
EM: kurt.feigl@pontos.cst.cnes.fr
AF: CNRS UMR 5562, 14, ave. E. Belin, Toulouse, 31400 France
AU: Pagli, C
EM: carolina@hi.is
AF: Institue of Earth Sciences, University of Iceland, Reykjavik, IS-101 Iceland
AU: Jonsson, S
EM: sj@erdw.ethz.ch
AF: Institute of Geophysics, ETH, Zurich, CH-8093 Switzerland
AU: de Zeeuw-van Dalfsen, E
EM: e.van.dalfsen@open.ac.uk
AF: Volcano Dynamics Group, Open University, Milton Keynes, MK7 6AA United Kingdom
AU: Vadon, H
EM: helene.vadon@cnes.fr
AF: CNES, 18 ave. E. Belin, Toulouse, 31055 France
AB: Crustal deformation events in Iceland in a variety of tectonic settings have been recognized using ERS1 and ERS2 images provided by ESA, including: (1) Intrusions in the Eyjafjallaj”kull volcanic system. Images spanning 1993-2000 identify considerable surface deformation in an area south of the Eyjafjallaj”kull icecap. The intrusive events (occurring in 1994 and 1999) have also been detected by tilt and GPS campaign measurements, as well as high seismic activity. Modeling based on InSAR data suggest a more complex source geometry than previous work based on GPS and seismic data. (2) Earthquake faulting in the SISZ due to seismic activity in June 2000 has been detected in several images. On June 17, and June 21, 2000 two Mw 6.5 earthquakes ruptured N-S striking faults in the SISZ. Joint inversion of InSAR and GPS data indicates that the two events activated faults 15 km long extending to about 9 km depth. Maximum slip, reaching more than 2 meters in both events, is concentrated in the upper crust, from the surface to 5-6 km depth. (3) Deformation due to dynamically triggered earthquakes on the Reykjanes Peninsula, about 80 km to the east of the main event in the SISZ (June 17, 2000 Mw 6.5 earthquake). Inverse modeling of the InSAR data estimates the deformation to originate from a Mw 5.8 and a Mw 5.3 event, when assuming uniform slip on two simple rectangular fault patches. (4) Subtle surface deformation signal in the vicinity of the main earthquake faults active in the June 2000 SISZ sequence have been documented in InSAR images. The deformation signals correlate well with water-level changes in geothermal wells and have been interpreted as poro-elastic rebound following the SISZ 2000 earthquakes. (5) An eruption at Hekla volcano began on February 26, 2000. Short-term precursory seismic activity was detected about one hour before the eruption started. Initially, a 6-7 km long eruptive fissure opened up along most of the Hekla ridge. Deformation due to the eruption is seen in a series of interferograms. The displacements appear to be the result of dike opening as well as subsidence due to deflation of a deep-seated magma chamber. (6) Surface inflation due to inflow of magma in the Hengill area can be seen in images spanning 1993 to 1998. The uplift signal can be explained by an expanding Mogi-source at 7 km depth, with 2-cm/year inflation rate. Persistent seismicity during 1994 to 1998 was associated with the widespread uplift. (7) Long-term subsidence in the Askja caldera has now been recognized not only by tilt and GPS, but also in InSAR images. A series of interferograms shows continuous subsidence, with the size of the deformation signal scaling well with the time span of the images. The subsidence can be partly related to cooling of a magma chamber. (8) Readjustment of the spreading segment at Krafla has been detected in InSAR images spanning 1992 to 2000. Subsidence occurs above an inferred shallow magma chamber, which fed events during the 1975 to 1984 rifting period. The subsidence is elongated along the spreading axis, which is interpreted to be due to cooling contraction and ductile flow of material away from the spreading axis. A wide-spread uplift signal of about 1 cm/yr has however been recognized to the north, and appears to be due to recharging of magma into a deep seated source. All the studies have benefited from images contributed by ESA PI contracts.
DE: 8123 Dynamics, seismotectonics
DE: 8159 Rheology--crust and lithosphere
DE: 7209 Earthquake dynamics and mechanics
DE: 1242 Seismic deformations (7205)
DE: 1243 Space geodetic surveys
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting