Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original Paper

Havíř

Orientations of the principal paleostress in the Western Bohemia sesmoactive region and their comparison with the recent stress

Journal of the Czech Geological Society, volume 50 (2005), issue 3-4, 133 - 142

DOI: http://doi.org/10.3190/JCGS.983

The palaeostress analyses based on the fault striae data were carried out in the Western Bohemia seismoactive region. The results of these analyses were compared with the recent orientations of the principal stresses determined from focal mechanisms of micro-earthquakes. The fault striae data were obtained mainly from the late-Variscan granites. No data for the palaeostress analyses were found in the post-Variscan (Tertiary) sedimentary cover. Five groups of solutions were determined. In the case of two solutions (solution A: NE-SW compression and NW-SE extension; solution D: NW-SE compression and NE-SW extension), the fault planes were orientated similarly to nodal planes of the focal mechanisms of the recent micro-earthquakes. During the Late Cretaceous to the Tertiary, the sense of shear movements along the active fault planes connected with solution A was opposite with respect to the recent faulting. The geometry of the active faults connected with the palaeostress field D was also similar to recent faulting including the sense of the shear. Thus, in the Western Bohemia seismoactive region, some of the recently active fault planes may represent reactivated pre-existing structures formed during earlier tectonic stages (palaeostress fields represented by solutions A or D).