Brixová B., Mojzeš A., Pašiaková M., Zubalová M., Bartošová A. & Bielik M., 2016: Velocity analysis and application of synthetic seismograms in the area of the Vranovice and the Nesvačilka troughs (Bohemian Massif). Acta Geologica Slovaca, 8, 1, 99–108.

Velocity analysis and application of synthetic seismograms in the area of the Vranovice and the Nesvačilka troughs (Bohemian Massif)

Bibiana Brixová¹, Andrej Mojzeš¹, Mariana Pašiaková¹, Miroslava Zubalová², Andrea Bartošová¹ & Miroslav Bielik^1,3

¹Comenius University in Bratislava, Faculty of Natural Sciences, Department of Applied and Environmental Geophysics, Mlynská dolina, Ilkovičova 6, SK-842 15 Bratislava, Slovak Republic; kytkova1@gmail.com
²MND a. s., Úprkova 807/6, CZ-69501 Hodonín, Czech Republic
³Earth Science Institute of the Slovak Academy of Sciences, Dúbravská cesta 9, 840 05 Bratislava, Slovak Republic

Abstract

The paper presents the results of velocity analysis performed in the Nesvačilka and Vranovice troughs. The troughs extend in the south-eastern part of the Bohemian Massif (the Moravian Block). As both belong to the most promising areas of the Bohemian Massif in the search for and production of hydrocarbons, their geological and geophysical survey is very important. Therefore, one of the key points is to determine the accurate data on the depth of the significant geological and stratigraphic units, which form the Nesvačilka and the Vranovice troughs. For this purpose the velocity analysis and the application of synthetic seismograms have been defined and applied. The results indicate that the lithostratigraphic units of the studied region are characterized by a large velocity interval. Based on the data from well log measurements (check shots) and synthetic seismograms the following velocities of seismic waves were determined in single lithostratigraphic units: 2.4–3.3 km/s in sediments of Flysch nappes, 2.7–3.6 km/s in the Palaeogene sediments, 3.3–4.3 km/s in the Jurassic sediments (3.7–5.1 km/s in carbonates and 3.5–4.8 km/s in pelites and conglomerates), 4–5.4 km/s in the Carboniferous sediments, and 4.6–6.6 km/s in the Devonian carbonates. Moreover, the synthetic seismograms and check shot results point to significant velocity interfaces. We discovered that: (a) within the sediments of Flysch nappes velocities in Menilitic Formation are higher than in the Submenilitic and the Ždánice-Hustopeče formations, (b) interface sediment of the Flysch nappes and Palaeogene deposits is characterized by a decrease of velocity, and (c) big contrast of velocity reflects the boundary between the carbonates (the Devonian and the Jurassic) and their surrounding rocks. The velocity analysis helps significantly for mapping of the Outer Carpathian Flysch nappes (the Pouzdřany Unit and especially the Ždánice Unit), the Neogene deposits, the Palaeogene deposits and the Devonian carbonates. All the knowledge we obtained has been used in detailed mapping and assessment of potential and confirmed hydrocarbon deposits in the studied area.

Key words: velocity analysis, check shot, synthetic seismogram, Nesvačilka Trough, Vranovice Trough, Bohemian Massif

Manuscript received: 2015-10-11

Revised version accepted: 2016-03-04