A „Kapos-vonal” középső szakaszának szerkezeti-mélyföldtani viszonyai és neotektonikai jellegei a legújabb geofizikai vizsgálatok tükrében

Abstract

The present study summarizes the results of the most recent geophysical research on the middle portion of the Kaposline (central Hungary). This work is dedicated to the memory of our unforgottable Colleague, Friend and Master, late Prof. Dr. Ferenc Horváth.As a first step a complex geophysical-geological database was formed integrating all available previous and newly measured 2D/3D reflection seismic, as well as borehole data, including also the results of new stratigraphic wells. A new, geologically and geometrically consistent 3D geological model of the study area was built by the interpretation of this integrated database. This 3D model consists of five geological horizons of basic importance within the study area (top pre-Cenozoic basement, top clastic/volcanic Lower Miocene, top marine Middle Miocene, top Endrőd and top Algyő Formations), as well as the interpreted faults. Considering the obtained new results, the previously published geologicalstructural models were critically re-evaluated and -if necessary -modified.One of the most important geological results of the research is the reambulation of the spatial extent, structural and facies relationships of the crystalline and Mesozoic basement rocks in the study area based on integrated evaluation of seismic and well data. Furthermore, the demonstration of the pronounced Early Miocene rifting event associated with the formations of several smaller basins with a depth up to 2 kilometers also represents a fundamental result. These basins were filled by a large amount of continental clastic sediments and coeval calc-alkaline volcanics. These findings underline the importance of the previously less known (and emphasized) role of the Early Miocene phase during the formation of the Pannonian basin.Based on the results of fault mapping the most important fault zones of the study area involve the ENE-WSW striking "Kapos line", furthermore the NE-SW striking Dunaszentgyörgy-Harta, and the Bonyhád fault zones, the latter mapped first during this research. All of these fault zones are characterized by steep dip (≥60-70°). The Bonyhád fault zone in the southwest joins to northern imbricate zone of the Mecsek Mts. The general fault pattern of the study area is characterised mostly by NE-SW striking faults being (sub)parallel to the mentioned major fault zones. Structurally less important, NW-SE striking faults occur mostly south of the "Kapos line".The results of detailed fault mapping clarified that a single, along strike structurally and geometrically uniform "Kapos line" does not exist in the study area. Instead, this fault zone can be divided into a western ("Kapos-W") and an eastern segment ("Kapos-E"), which differ both in dip direction and -in accordance with previous literature dataobserved neotectonic activity. The eastern "Kapos line", the Dunaszentgyörgy-Harta and the Bonyhád fault zones all show pronounced neotectonic activity. Moreover, they form the most important elements of a regional-scale, broad, neotectonic sinistral strike-slip shear zone consistin...

Conservative Evaluation of Fault Displacement Hazard for a Nuclear Site in Case of Insufficient Data on the Fault Activity

“…The faults were mapped based on 2D and 3D seismic surveys. The fault traces are shown in Figure 1a (see also in [3,21,22]). The S-W end of the fault F_II_N crosses the site, and F_II_S is close to the site.…”

“…The micro-seismic monitoring, which has been running for 30 years, does not indicate activity, and the GPS monitoring does not show a deformation tendency either. The basic information on the geology, neotectonics, and seismicity of the mid-Pannonian region and the site vicinity area is given in [3,21,22,24,29]. The mapped lengths of these faults (LF) are 26.85 and 27.9 km, respectively.…”

“…The third model is the modified SHARE model, where SHARE zone-04 is split by the Hungarian experts into zones 04A and 04B to better account for the mid-Hungarian fault system. This is based on the newest interpretation of the neotectonics of the Pannonian Basin [21,29], and on the experience of seismotectonic modelling [30].…”

“…In 2016, full-scope site investigations were performed for a new plant at the same site, including accurate mapping of the faults, extensive paleo-seismic investigations, and trenching over the mapped fault that crosses the site. The trenching at the site area provided evidence for some liquefaction-induced ground failure of the soil profile, which happened about 20 ka ago and was repeated with a time gap of about 1 ka [21,22]. Unfortunately, this information is insufficient for quantitatively evaluating fault activity.…”

Safety of Nuclear Power Plants with Respect to the Fault Displacement Hazard

“…There are sites where the assessment of the activity of the mapped faults in the site vicinity or even within the site location cannot be assessed due to specific geologic context. There, the simple presence of the fault suggests suspicion of the capability, see examples in [16,17], and the doubts are inevitably considered as an issue in nuclear safety.…”