Tectonic pattern of the Hronov-Porici trough as seen from pole-dipole geoelectrical measurements

The Hronov-Porici Trough represents the easternmost part of the Trutnov-Nachod Depression. The NW-SE striking structure was formed due to the post-Cretaceous flexural folding and is filled with the Upper Cretaceous sediments. Both the NE and SW margins of the trough are bounded by flexures with the Upper Cretaceous strata dipping 40-60° towards the axis of the trough. The NE flexure is situated close to the parallel Hronov-Porici Fault Zone. Up to now, it is not fully known, in what extent the normal faulting was involved in the evolution of the structure. From the geomorphological point of view, the normal fault constraints of the trough seem to be acceptable, as the surface topography of its present margins exhibit many signs typical for fault scarps. However, the existence of a fault system bounding all round the Hronov-Porici Trough has not been proved by any geological research. Hence the geophysical research was carried out on both sides of the NW part of the trough to support one of these hypothesis. Five geoelectrical profiles were measured in the area and the fault system was proved on the NE side of the trough. On the SW boundary the fault system was not found. Thus it seems, that the NE boundary is controlled by fault tectonics, whereas the SW boundary is rather formed by a simple flexure. KEYWORDS: Hronov-Porici Trough, Hronov-Porici Fault Zone, electric resistivity measurements, geomorphology, normal faulting