Open AccessPostseismic deformation following the June 2000 earthquake sequence in the south Iceland seismic zone
Author(s) -
Árnadóttir Thóra,
Jónsson Sigurjón,
Pollitz Fred F.,
Jiang Weiping,
Feigl Kurt L.
Publication year - 2005
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2005jb003701
Subject(s) - geology , seismology , viscoelasticity , deformation (meteorology) , crust , mantle (geology) , geodesy , global positioning system , poromechanics , geophysics , geotechnical engineering , telecommunications , oceanography , physics , porous medium , porosity , computer science , thermodynamics
We observe postseismic deformation on two spatiotemporal scales following M w = 6.5 earthquakes in the south Iceland seismic zone on 17 and 21 June 2000. We see a rapidly decaying deformation transient lasting no more than 2 months and extending about 5 km away from the two main shock ruptures. This local, month‐scale transient is captured by several radar interferograms and is also observed at a few campaign GPS sites located near the faults. A slower transient with a characteristic timescale of about a year is detected only by GPS measurements. The month‐scale deformation pattern has been explained by poroelastic rebound due to postearthquake pore pressure changes. In contrast, the year‐scale deformation can be explained by either afterslip at 8–14 km depth or viscoelastic relaxation of the lower crust and upper mantle in response to the coseismic stress changes. The optimal viscoelastic models have lower crustal viscosities of 0.5–1 × 10 19 Pa s and upper mantle viscosity of ∼3 × 10 18 Pa s. Because of the limitations of our GPS campaign data, we consider both afterslip and viscoelastic relaxation as plausible mechanisms explaining the deformation field. Both types of postseismic deformation models suggest that the areas of large coseismic stress increase east of the 17 June and west of the 21 June ruptures continue to be loaded by the postseismic deformation.