GEOMORPHOLOGICAL DATA FROM THE POTENTIALLY ACTIVE HLUBOKA FAULT IN THE NEAR-REGION OF THE NPP TEMELIN (BUDEJOVICE BASIN, SOUTHERN BOHEMIAN MASSIF)

The NW-striking Hluboká-Fault System is a potentially active fault in the southern Bohemian Massif forming a “disputed seismic source” in the vicinity of the nuclear power plant of Temelin. The Variscan fault was repeatedly activated in Mesozoic to post-Miocene times forming the NE margin of the Budějovice Basin, which is filled with up to 340m thick Cretaceous to Miocene sediments. Part of the fault is characterized by a prominent linear morphological scarp.

Quantitative morphological indices compare the scarp of the potentially active fault with slopes, which are not fault-controlled. Analyses use morphological parameters of small ephemeric tributaries of the Vltava River, which are all similar with respect to their catchments, hydrological conditions and location in crystalline basement rocks. Morphological differences in valley shapes are therefore likely to result from different amounts of uplift of the catchments with respect to the Vltava River. All parameters were measured from a 10m resolution DEM and digital topographic maps 1:10.000. Additional field measurements were made at locations where the resolution of the digital data is insufficient.

Data show an extremely low mountain-front sinuosity of the hillslope forming the footwall of the Hluboká Fault characterizing a very straight mountain front at the fault. The values are significantly smaller than those observed at the other analysed mountain-piedmont junctions. Analyses of streams use the ratio of valley floor width to valley height (Vf), stream-length gradients (SL), thalweg sections and basin elongation ratios. The mountain slope at the fault scarp shows deep and narrow V-shaped valleys with streams that are actively incising probably responding to continuous uplift. Vf and SL values are generally lower than those obtained from drainages not crossing the fault. Marked differences are further evident from thalweg sections. The creeks off the fault generally show simple concave-up profiles while streams crossing the fault show marked convex-up knickpoints close to the fault.

In conclusion, the quantitative geomorphologic data consistently indicate that the crystalline massif in the footwall of the Hluboká Fault is actively uplifting with respect to the Budějovice Basin in the hangingwall of the fault.