HR: 0800h
AN: S11B-0554    [Abstracts]
TI: A Low-velocity Finger from Iceland beneath Southern Scandinavia - the Key to Understanding Neogene Uplift?
AU: * Weidle, C
EM: christian.weidle@geo.uio.no
AF: Dept of Geosciences, University of Oslo, P.O.Box 1047, Blindern, Oslo, 0316, Norway
AU: Maupin, V
EM: valerie.maupin@geo.uio.no
AF: Dept of Geosciences, University of Oslo, P.O.Box 1047, Blindern, Oslo, 0316, Norway
AB: A model of upper mantle S-wave velocity beneath northwestern Europe is presented, based on a tomography of regional surface wave observations. Data from international and, more importantly, regional data archives (including temporary deployments) were used to measure group velocities for both Love and Rayleigh surface waves. The procedure for data selection, group velocity measurements and inversion for group velocity 2-D maps follows closely the one described by Levshin et al. (GJI, 170, 441-459, 2007). Our new set of group velocity maps differs significantly from global reference maps, enhancing many details and amplitudes of group velocity variations in the study region. We then apply a linear inversion scheme to invert for 1-D shear wave velocity profiles which are assembled to a 3-D model. By choosing conservative regularization parameters in the 2-D inversion we ensure the smoothness of the group velocity maps and the resulting 3-D shear wave speed model. To account for the different tectonic regimes in the study region, we compare inversions with 3 different reference models (pure 1-D, 3-D crust / 1-D mantle and pure 3-D) to investigate the sensitivity of the 1-D inversions to inaccuracies in crustal models. We find that all three models are consistent at depths below 90 km and the resulting models deviate only slightly from each other, mostly in amplitudes. We image an intriguing low-velocity anomaly extending from the Iceland plume domain across the north Atlantic beneath southern Scandinavia between 70-150 km depth. Beneath southern Norway, the negative perturbations reach a maximum of up to 13 % w.r.t. ak135 and a shallowing of the anomaly is indicated. This observation could explain the sustained uplift of southern Scandinavia in Neogene times, but the mechanisms are yet undetermined. Furthermore, our upper mantle model reveals good alignment to ancient plate boundaries and first-order crustal fronts around the triple junction of the Baltica-Avalonia-Laurentia collision in the early Paleozoic.
DE: 7208 Mantle (1212, 1213, 8124)
DE: 7218 Lithosphere (1236)
DE: 7255 Surface waves and free oscillations
DE: 7270 Tomography (6982, 8180)
DE: 8175 Tectonics and landscape evolution
SC: Seismology [S]
MN: 2007 Fall Meeting