REDISTRIBUTION OF RECENT COLLISION PUSH AND RIDGE PUSH IN CENTRAL EUROPE: INSIGHTS FROM FEM MODELLING

Abstract

2-D elastic finite element models of the recent stress field of Central Europe are built to evaluate the loads exerted on the continental boundary and the magnitude of tectonic stresses within the continental part of the plate. The models comprise 24 tectonic blocks (their stiffness is either constant throughout the model or varies from block to block), 16 fault zones and 12 geologically significant boundary segments. We have obtained a relatively unique balance of external tectonic forces by (1) careful adjustment of calculated stress directions and regimes to complex pattern of stress from data and (2) by calibration with gravitational potential energy. A high level of compression (ca. 9 × 1012 N m-1) exerted to the short Ionian side of the Adriatic indenter is crucial for the stress-field pattern in Central Europe. The Adria microplate rotates due to eccentricity between the Africa push from the south and the Alpine buttress to the north. A free boundary of the Apennines does not contribute significantly to this motion. Kinematics of this indenter is controlled by friction on the Dinaric suture, which, in turn is decisive for strain-energy distribution between the Alpine and the Pannonian domains. The predicted pronounced extension in the Greece-Aegean segment (2.5 × 1012 N m-1) implies active pull transferred from the Hellenic subduction zone. This extension releases stress in the Balkan-Pannonian region and enables the eastward escape of tectonic blocks in front of advancing Adria. Significant changes of tectonic push trends are found along the Black Sea-Caucasus boundary segment and at the European passive margin from the North Sea to the Arctic Ocean. Differential stresses in Central Europe are estimated in the range of 10-60 MPa when averaged over the 30-80-km-thick mechanically heterogeneous lithosphere. The maximum stiffness contrast across the model is predicted to be of one order of magnitude. Apparent friction coefficients of fault zones differ between the North European part of the plate (0.4-0.7), the Pannonian region (0.15-0.25) and the Dinaric suture (0.55). © 2006 The Authors Journal compilation © 2006 RAS.