M26

G. F. Panza*, St. Mueller**

*Istituto di Geodisia e Geofisica, Università di Bari, 1-70122 Bari, Italy

** ETH-Geophysics, CH-8093 Zurich, Switzerland

A structural model has been derived for the lithosphere-asthenosphere system in the European-Mediterranean area which is chiefly based on seismological data. Large lateral variations have been detected whose cause must primarily be sought in the collision process between the African and Eurasian plates. The collision front extends into the Alps through the Adriatic-promontory of the African plate. An attenuated lithosphere underlies the "Central European Rift" which extends from the North Sea to the Golfe du Lion. Scandinavia exhibits a remarkable difference by the almost total absence of an asthenospheric low-velocity layer. The main conclusion is the necessity to critically review the schematic plate tectonic models advanced so far to explain the complex history of evolution. If the main earthquake activity (m>,6.5) is correlated with the lithospheric properties a surprisingly clear picture emerges. The largest shocks tend to occur where the thickness of the lithosphere changes rapid1y in a lateral direction while the rigidity remains close to values found in stable areas. In regions where there is a significant reduction in rigidity (as e.g. in areas of tension), the occurrence of strong shocks is great1v diminished.