Quaternary activity of the Hluboká Fault
Petr Špaček1, Ivan Prachař2, Jan Valenta3, P. Štěpančíková3, J. Švancara1, J. Piskač2, J. Pazdírková1, R. Hanžlová1, J. Havíř1 and J. Málek2
1) Institute of Earth Physics MU Brno
2) Energoprůzkum Ltd. Praha
3) Institute of Rock Structure and Mechanics ASCR
Below are links to the abridged translation of updated final report for the research project "Paleoseismology of the fault structures near NPP Temelín". The research was funded by the State Office for Nuclear Safety (VaV project No. 1/2009; Jan 2009 to Dec 2010) and carried out in a co-operation of three independent institutes.
We performed a detailed study of the Hluboká Fault, a conspicious marginal fault of Cretaceous sedimentary basin with distinct morphology, located in the area of Temelín Nuclear Power Plant. The main objective was to assess the present-day tectonic potential of the fault and to get new data which would serve as a basis for the revision of regional seismic hazard in South Bohemia. Extensive amount of data relevant for the assessment of Quaternary slip in the fault zone was gathered at several localities on different fault segments, using observations on surface, in trenches, geophysical sections and boreholes, and dating of sediments overlying the fault zone.
Numerous observations of continuous stratigraphy of Miocene, Pleistocene and Holocene sediments across the fault zone suggest a long-term tectonic quiescence at the Hluboká Fault. In some trenches it was proved that the morphological escarpment associated with margin of the Budějovice basin is not linked with any active fault which continues into Miocene and Quaternary sediments. The present-day morphology of the escarpment is explained mainly as due to the differential erosion of unconsolidated sediments of the basin fill and long-term, probably multiphase, degradation of the fault scarp since Tertiary.
In central segment of the fault some young OSL dates of higher sedimentary relics of apparently alluvial origin are in conflict with the constant thickness of the lower terrace of the Vltava river across the fault. We propose an additional research which will bring more data and help resolve these ambiguities.
Revision of catalogues of historical and instrumental records of regional seismicity performed in this project indicate only minor activity with magnitudes not exceeding MI=3.2 in period 1591-1991 and ML=2.6 in period 1991-2009. The Hluboká Fault has not produced any recorded seismic events within the period of observation and is regarded as seismically inactive.
This report can be cited as: Špaček et al. (2011): Quaternary activity of the Hluboká Fault. - Unpublished report MU Brno, 199pp + appendices.
Appendix 3.1 - List of references used for compilation of macroseismic catalogue
Appendix 4.2-1 - Geophysical survey measurements
Appendix 4.2-2a - Borehole lithological profiles
Appendix 4.2-2b - Photographs of drilling cores