Abstract
INTERACTION of the elastic lithosphere with the underlying anelastic asthenosphere causes strain to propagate along the Earth's surface in a diffusion-like manner following tectonism at plate boundaries. This process transfers stress between adjacent tectonic segments and influences the temporal tectonic pattern along a plate boundary. Observations of such strain transients have been rare, and have hitherto been confined to strike-slip and underthrusting plate boundaries1. Here we report the observation of a strain transient at the divergent (spreading) plate boundary in Iceland. A Global Positioning System survey undertaken a decade after an episode of dyke intrusion accompanying several metres of crustal spreading reveals a spatially varying strain field with the expected diffusion-pulse shape and an amplitude three times greater than the 5.7 cm that would be expected from the average spreading rate2. A simple one-dimensional model with a thin elastic layer overlying a viscous layer fits the data well and yields a stress diffusivity of 1.1 á±0.3 m2s−1. Combined with struc-tural information from magnetotelluric measurements, this implies a viscosity of 0.3−2 × 1019 Pa s—a value comparable to that derived for Iceland from post-glacial rebound23, but low compared with estimates for mantle viscosity obtained elsewhere3.
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Foulger, G., Jahn, CH., Seeber, G. et al. Post-rifting stress relaxation at the divergent plate boundary in Northeast Iceland. Nature 358, 488–490 (1992). https://doi.org/10.1038/358488a0
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DOI: https://doi.org/10.1038/358488a0
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