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During the past 3 decades, several seismological techniques have been used to explore the deep structure of Europe. Profound lateral variations in the lithosphere-asthenosphere system became immediately apparent from the observed delay of teleseismic P-waves. On the basis of a uniform dispersion analysis of all the presently available long-period Rayleigh wave observations and applying a new method of regionalization, a map outlining the thickness of the elastic lithosphere in Europe could be constructed.
Regions of markedly thinned lithosphere are the Tyrrhenian and Balearic basins of the western Mediterranean Sea. Another extensional structure of particular interest is the "Central European rift system," which extends from the western Alps to the North Sea. In contrast, an increased lithospheric thickness has been found beneath the Betic Cordillera and the Alps which must be ascribed to underthrusting and subfluence leading to the formation of a pronounced lithospheric "root" reaching to a depth of about 200 km. Long-range seismic refraction profiles have permitted insight into details of upper mantle structure to depths of nearly 400 km in a few tectonic provinces.
Travel-time and amplitude data obtained in crustal seismic refraction experiments, supplemented by wide-angle and near-vertical reflection observations, have made it possible to study the major features within the continental crust of Europe. Regions selected for detailed studies include the southern part of the Iberian Peninsula, the Pannonian basin, the Rhine graben rift system, the northern Alpine foreland, and the Alps.
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