Ocena pionowych ruchów skorupy ziemskiej w Polsce południowo-zachodniej w świetle polowych materiałów niwelacyjnych

Abstract

Przedstawiono metodę opracowania polowych materiałów niwelacyjnych, przy wyznaczaniu ruchów skorupy ziemskiej na obszarze Polski południowo-zachodniej, wykorzystując polowe wyniki niwelacji precyzyjnej z lat 1879–1882 i 1952–1956.

Na podstawie opracowanych map wyróżniono obszary podnoszenia i obniżania.

Obniżanie się Sudetów Zachodnich stoi w sprzeczności z obserwacjami geologów i geomorfologów. Jest to spowodowane przeprowadzaniem ciągu niwelacyjnego wzdłuż głównego uskoku śródsudeckiego, na linii którego teren się obniża. Badania ruchów współczesnych wymagają pomiarów wzdłuż ciągów niwelacyjnych zaprojektowanych przez J. Oberca (1977).

ESTIMATION OF VERTICAL CRUSTAL MOVEMENTS IN THE SOUTH-WESTERN

POLAND IN THE LIGHT OF FIELD LEVELLING DATA

The field data from precise levelling surveys from the years 1879–1882 and 1952–1956, not distorted by equalization, were analysed. A detailed evaluation of quality of the used geophysical material is given. Nonrandom errors were traced in archival levelling material and eliminated. The elimination of these errors from the process of equalization resulted in reduction of the scale of mean errors in estimations of movements by half and, therefore, it limited deformations of the remaining levelling material.

Figure 2 presents time map of vertical movements of the Earth crust in south-western Poland, and Figure 3 – map of velocities of translocations of bench marks in this area. The former was made by geometric interpolation of movement velocity isolines between points with known values of vertical movements. It is, therefore, mainly of informative value, showing main trends of movements in the studied area. It forms a basis for selecting places where recent crustal movements should be studied in special geodynamical polygons. The studied area is divided into numerous WNW–ESE to WE trending horsts and troughs by neotectonic (Young Alpine) movements. They are cut by NW–SE oriented Marginal Sudetic Fault, along which the Sudety Mts were uplifted (J. Oberc, S. Dyjor, 1969; J. Oberc, 1972, 1975). These forms are clearly visible in the field which indicates that the neotectonic movement of blocks still continues.

However, only Biała Głuchołaska dislocation and some faults from the vicinities of Kłodzko are reflected by isolines of recent crustal movements. The lack of any distinct reflection of the neotectonics on the map of recent crustal movements results from the fact that the basic levelling networks were not aimed at tracing recent crustal movements nor their nature. For example, in mountain areas such network was led along valleys, a part of which have tectonic foundations.

The Kamienna Góra Lubań traverse going along the Intra-Sudetic Fault is the best example here as downwarping along this line effects the image of strongly uplifted Karkonosze-Izera block, presented as a depressed area on the maps of recent crustal movements. Therefore, a new precise levelling network is needed for studies on recent crustal movements. A project of such network was prepared by J. Oberc (1977) and new studies may be initiated after discussions on validity of premises of that project.