Seismicity, geology, seismotectonics and geodynamics of Tereblya-Ritska HPS area (Ukrainian Transcarpathians)
Journal Title: Геодинаміка - Year 2016, Vol 20, Issue 1
Abstract
Purpose. The aim of the work is to conduct the complex analysis of seismicity, geology, seismotectonics and difference scale geodynamic processes in the Tereblya-Rika hydro power station (HPS) area in the Ukrainian Transcarpathians (23.35-23.87ºS, 48.23-48.51ºN) to refine estimation of geo-ecological risks. Methods. Research methodology includes comprehensive analysis of seismic, geological and geodetic data, including those involving modern techniques and the latest research results, including data on seismicity of Carpathian region of Ukraine during the historical period and the period of instrumental observations, new methods of analysis of macroseismic fields and Transcarpathian earthquakes fosi refinement, analysis of geology and tectonics of widespread here nearsurface thrust nappes, geomorphological analysis of relief features and modern relief generating processes, special (including monitoring) geodetic surveying research (triangulation and optical range finder measurements, GPS-studies) and an analysis of obtained data. Results. According to geological and tectonic data Tereblya-Rika HPS is located on geological structures of Burkut (Porkulets) nappe of the Ukrainian Carpathians, about 2 km south of the line of his contact with Duklya-Chornogora (Duklya) nappe. HPS zone is at a distance of 16–18 km north-east of the Transcarpathian seismically active deep fault (suture) and at a distance of 28–30 km from the junction of him with also seismoactive Oash meridional fault of Transcarpathian depression. By results of seismological studies in the West of area (at 23.43±0.03ºS) the submeridional depth (from earthquake to 38–52 km depth) seismotectonically active zone of contact of terrane Alkapa and Tisza-Dacia in the Carpathian region of Ukraine is traced. In the south and southeast the seismically active (activity to 31 km depths) is diagonal (northwest – southeast direction, az. 117 ±5º) Transcarpathian deep fault zone. The central part of the zone (HPS reservoir area) is relatively low seismically active. By macroseismic data the HPS and reservoir area undergo by seismic shakings with intensity to 3–4 points from historical 1935 Chumalovo and 1937 Drahovo earthquakes and from 1978 Uhlya and 2011 Kolochava earthquakes. Seismic activity of available here near surface (0-6 km) geological structures – thrust nappes is relatively low (13 weak earthquakes with M=0,8–2,2 on 26×30 km territory during 55 years). In adjacent to the Transcarpathian deep fault zone the “seismic focal surface” (plane) was traced, which fall down from the fault zone (from the depth of 6 km) at an 57±2º angle in the north-east under the Carpathian structures (to a depth of 32 km) and it is an indicator of current residual activity of the process of so-called “crocodile tectonics” in the Carpathian region of Ukraine. Originality. For the first time a detailed comprehensive analysis of seismicity, geology, seismotectonics and difference scale geodynamic processes in Tereblya-Rika HPS area was carried out. The main features of deep-spatial distribution of seismic activity in the area, in particular, the presence of “seismic focal surface” (plane) that extends approximately 110º azimuth along the Transcarpathian deep fault (at a 8–10 km distance in south from the HPS site) fall down from him under the Carpathians (from depths of 5–6 km to depths of 20–30 km) with the dip angle of about 57º, that clearly illustrates the inherited decreasing activity of so-called “crocodile tectonics” processes in the region. Also the presence of “seismic lull” zone for M≥1 earthquake within 7–9 km radius from HPS site for the period of instrumental observations (since 1961) and within 15 km radius for earthquakes with M≥2,5 for last 170 years. Realized (3–4 points over last 170 years) and predicted (5–7 points) seismic shakings intensity for HPS site was estimated. The connection of local seismic activity with available here at depths of 10-11 km zones of increased conductivity in the Earth's crust was traced. Practical significance. The research results make it possible to assess the possible seismic and deformation influences on Tereblya-Rika HPS constructions and reservoir, to develop on this basis a project of geophysical and geodetic geodynamic monitoring in the site HPS area with the aim of detailed study of multiscale geodynamic processes in the area and development the necessary engineering measures to ensure reliable and ecologically safe operation of HPS.
Authors and Affiliations
A. Nazarevych, L. Nazarevych, V. Shlapinskyy
Keywords
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- EP ID EP194458
- DOI 10.23939/jgd2016.01.170
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