Application of the precision levelling method to evulate the vertical movements within eastern part of the Elbe fault system (SW Poland, western Sudetes)

Abstract

The eastern part of the Elbe Fault System covers an area of the Bohemian Massif located between the middle Odra faults in the north, and the system jumps to the south of the Elbe edging the Bohemian Cretaceous Basin on the orientation of NW-SE to WNW-ESE. The Sudetic horst is located in the middle part of this area, and within it there are distinguishable, smaller tectonic forms that arise after the Cretaceous-Paleogene inversion. In this part of the Western Sudetes, the Nysa Klodzka Graben is clearly marked, and surrounding it, horst formations: Bardo Mountains, Zlote Mountains, Śnieznik Massif, Orlickie and Bystrzyckie Mountains. In this part of the Sudetes there are many more complementary faults with directions of NNW-SSE or NNE-SSW. The lack of correlative deposits makes difficult to identify stages of the Nysa Klodzka Graben tectonic development. However, it is estimated that since the Miocene until today, displacement between the bottom of the graben, and the surface of the Śnieznik Massif peak had an amplitude about of 1000-1200 m. On the basis of indirect evidence, it can be assumed that since the late Miocene to the present, the northern border of the graben has increased by about 50 m and the southern, by about 15 m. Numerous gorges and places of an occurring lattice system of river valleys indicates that this area is still little changed as a result of tectonic movements. Weak seismicity of the area is recorded in the historical documents, and now recorded by the seismic stations. Satellite measurement campaigns (GNSS) conducted in this area during the last 20 years confirm the trend of vertical movement points. They also point to the diversity (velocity and directions) of horizontal displacements (Kaplon et al., 2014). Attempts to determine the scale of the vertical displacements in repeated precision levelling lines confirm the relative displacement occurring between the bottom of the Nysa Klodzka Graben and its metamorphic frame, and also indicate weak tectonic movements that occur within the graben bottom. ARTICLE INFO