HR: 1340h
AN: U43B-0834    [Abstracts]
TI: Post-rifting deformation of North Iceland and its implication for Mid-Oceanic Ridges
AU: * Qin, R
EM: rqin@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 RT 9W, Palisades, NY 10964 United States
AU: Buck, W R
EM: buck@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 RT 9W, Palisades, NY 10964 United States
AB: Post-rifting deformation of North Iceland after the 1975-1984 Krafla dike episode has been monitored by GPS, ground tiltmeters and satellite radar interferometry. The horizontal displacement in the region tens of kilometers across Krafla rift zone is several times higher than the average plate spreading rate and is well explained by post-rifting stress relaxation. The vertical displacement during 1987-1992 period has up to ~11cm uplift near the rift zone and ~3cm subsidence ~50km away from the rifting axis. After 1992 till 1999 the region in vicinity of the rifting zone has centimeter-level subsidence per year. Previous post-rifting relaxation models failed to explain this complex history of vertical deformation and here we present a numerical model that couples the brittle deformation of the lithosphere and viscoelastic relaxation of the underlying asthenosphere to explain it. We propose that 1975-1984 Krafla dike intrusions uplifted the flanks instantly and changed the vertical stresses at the bottom of lithosphere, thus generating a bending moment. As the asthenosphere relaxes, the lithosphere is bent up producing uplift at the surface close the axis and subsidence away from the axis. After a characteristic Maxwell relaxation time, the viscoelastic deformation is in its final stage and the surface deformation will be dominated by tectonic stretching due to the divergence of the plate, which causes the surface to subside. The competition between tectonic stretching and post-rift relaxation are expected to exist in submarine Mid-Oceanic Ridges too, except that the different lithosphere thickness and plate spreading rates, as well as the presence of magma sill along the ridge axis may change the deformation pattern. We show numerical results for different idealized MOR structures and suggest submarine geodetic monitoring is needed to test our model.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 3035 Midocean ridge processes
DE: 8150 Plate boundary: general (3040)
DE: 8178 Tectonics and magmatism
DE: 8416 Mid-oceanic ridge processes (1032, 3614)
SC: Union [U]
MN: Fall Meeting 2005