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Mapping Tectonic Deformation in the Crust and Upper Mantle Beneath Europe and the North Atlantic Ocean

Science  23 Aug 2013:
Vol. 341, Issue 6148, pp. 871-875
DOI: 10.1126/science.1241335

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European History at Depth

The preferential alignment of mineral grains as a result of flow direction can polarize seismic waves traveling through Earth's interior, based on velocity and direction. Zhu and Tromp (p. 871, published online 8 August) mapped this anisotropy beneath the European continent and the North Atlantic Ocean—which are products of several tectonic events across varying temporal and spatial scales—using seismic tomography. The model generated correlates well with plate motion in the region, and, compared to geodetic measurements, much of the anisotropic features are consistent with modern strain rates. Some features below Eastern Europe, however, appear to be remnants of tectonic events that occurred over 350 million years ago.

Abstract

We constructed a three-dimensional azimuthally anisotropic model of Europe and the North Atlantic Ocean based on adjoint seismic tomography. Several features are well correlated with historical tectonic events in this region, such as extension along the North Atlantic Ridge, trench retreat in the Mediterranean, and counterclockwise rotation of the Anatolian Plate. Beneath northeastern Europe, the direction of the fast anisotropic axis follows trends of ancient rift systems older than 350 million years, suggesting “frozen-in” anisotropy related to the formation of the craton. Local anisotropic strength profiles identify the brittle-ductile transitions in lithospheric strength. In continental regions, these profiles also identify the lower crust, characterized by ductile flow. The observed anisotropic fabric is generally consistent with the current surface strain rate measured by geodetic surveys.

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