Geo-hidrodinamika: folyadékdinamikai jelenségek a Föld belsejében = Geo-hydrodynamics: fluid dynamical phenomena in the Earths`s interior

Projektünk célja a Föld belsejében zajló többféle áramlás közül két rendszer vizsgálata volt. A köpenyben zajló termikus konvekció háromdimenziós numerikus modelleredményei feltárták, hogy a vizsgált paraméterek mindegyike befolyásolja a köpenyhőoszlopok számát. A hőoszlopok dimenziótlan területi sűrűsége 2-3 illetve 0,04-0,06 attól függően, hogy a feláramlás a köpeny-mag határról indul vagy a modell kétréteges, és a felsőköpeny hőoszlopok forrástartománya a 660 km-es fázishatár. Szuperkritikus Rayleigh-szám esetén, belső hőtermelés jelenlétében a területi sűrűség értéke ~1. Ezeket az eredményeket a hotspot-listákkal összevetve arra a következtetésre juthatunk, hogy az áramlási rendszer nem tökéletesen egyréteges, a hotspotok alatti feláramlások forrástartománya részben a köpeny-mag határ, részben azonban a 660 km mélységű termikus határréteg lehet. Porózus közegben történő vízáramlás modellezésével megállapítottuk, hogy nagy Rayleigh-szám és kis hidraulikus gradiens esetben poligonális konvekciós cellák alakulnak ki, míg kis Rayleigh-szám és nagy hidraulikus gradiens határesetben egyetlen cellában zajlik a konvekció. Különösen érdekes az eredmény az átmeneti értékeknél, amikor lejtőirányú vagy arra merőleges konvekciós hengercellák alakulnak ki. E "kombinált" áramlási képre a légköri áramlásoknál és Földköpeny konvekciós jelenségei között is találhatunk analógiákat. A felszínközeli térrészek vízáramlásának modellezésében esettanulmányokkal egészítettük ki vizsgálatainkat. | The main goal of our OTKA project was to investigate two types of convection in the Earth's interior. The 3D modeling of mantle convection showed that all the investigated model parameters (Rayleigh number, depth-dependent viscosity, heat production) affect the number of mantle plumes. The areal densities of plumes are 2-3 or 0.04-0.06 depending on the source area of upwelling plumes i.e. the mantle-core boundary or the phase boundary at depth of 660 km, respectively. In case of supercritical Rayleigh number the plume density is ~1. To compare these results with several hotspot lists we can conclude that the source area of mantle plumes are partly the mantle-core boundary and partly the thermal boundary layer at 660 km depth. The numerical modeling of underground water flow in the porous-permeable layers of the crust showed that high Rayleigh number and low hydraulic gradient result in a number of polygon shape convection cells and low Rayleigh number and high hydraulic gradient result in one convective cell. In case of intermediate parameters cylindrical convection cells develop parallel or perpendicular to the slope. Similar circulations can be observed in the atmosphere and in the Earth?s mantle in certain conditions. The results of this modeling were used to interpret groundwater flow observations in the Pannonian basin

Heat Flow Density Determinations in Hungary Using Well Logs

The thermal conductivity of rocks can be deduced from available data of explora-tion wells such as core samples, cuttings, lithological descriptions and geophysical well logs. As the thermal conductivity of clastic sediments is lower than the conductivity of the crys-talline basement, the sediments have a significant influence on the temperature distribution and heat flow density. We present a methodology for determining the thermal conductivity of clastic sediments using geophysical well logs and thermal conductivity data measured in laboratory. Our results are based on the data of 6 exploration wells. Several well log combi-nations and thermal conductivity measurements from 70 core samples were used to work out the method. The lithological composition consisting of shale, sand and water was identified and the volumetric fractions of these components were derived from wireline logging data such as natural gamma ray, resistivity, bulk density and neutron porosity logs. The litholo-gical composition was determined with Bayesian inversion applying the weighted least squares method. The effective thermal conductivity was computed by applying an appropri-ate mixing law using the thermal conductivity values of the lithological components. The thermal conductivities derived from well logs were tested and new matrix thermal conduc-tivity values were calculated using archive thermal conductivity measurements of core sam-ples. The harmonic mean model proved to be the best mixing law, resulting in the best fit to laboratory measurements. The reliability of our model was also tested with the help of tempe-rature measurements carried out in a well. Heat flow density determinations were carried out using the Bullard-plot technique with thermal conductivities calculated by our new method. In case of 6 wells, heat flow densities calculated by the new method are in the range of heat flow density values previously conducted but with substantially lower uncertainties

Possibilities and limitations in the utilization of the Neogene geothermal reservoirs in the Great Hungarian Plain, Hungary

Abstract Hungary has favorable geothermal conditions. The paper discusses the thermal and hydrogeologic conditions of the Neogene groundwater reservoir below the Great Hungarian Plain. In the exploration of the reservoir one of the most problematic issues, is the interaction between gravity-driven and overpressured flow regimes, especially along conductive faults. A combination of structural geology supported by seismic interpretation, hydrogeochemistry, and hydraulic evaluations can help to delineate the two flow regimes and determine the origin of the water: meteoric (and thus rechargeable) or syn-sedimentary (and thus non-rechargeable) pore water. These results can be incorporated into basin-scale digital models of the Neogene reservoir. The models can be used to predict the response of the reservoir to the water production and injection, and can help to exploit more efficiently and sustainably the thermal waters of the Great Hungarian Plain reservoir

A Tihanyi Formáció a Balaton környékén: típusszelvény, képződési körülmények, rétegtani jellemzés.

Revisiting the Tihany, Fehérpart section, overviewing archive data, comparison with successions of nearby wells, well-logs, stratigraphic data and results of the high-resolution seismic surveys on Lake Balaton resulted a coherent picture on the depositional environment, age, stratigraphic correlation and palaeogeographic connections of the Tihany Formation. In addition to former analyses of grain-size distributions, carbonate and clay content, the sedimentary structures were investigated, a pilot study of gamma-ray measurements on the field was carried out and several orders of cyclicity were demonstrated. Besides previous palaeontological studies new fossils were collected, determined and magnetic polarity of the rocks were measured. The Tihany, Fehérpart section is correlated with the Spiniferites tihanyensis dinoflagellate, the MN11 micromammal and the Limnocardium decorum sublittoral mollusc biozones. It shows normal magnetic polarity. It is underlain by open lacustrine, reverse polarity shales of the Congeria praerhomboidea zone, and is overlain by layers indicative of the Prosodacnomya zone. The latter is well definied by the radiometric age (7.9 Ma) of the overlying volcano sedimentary suite. Therefore the Fehérpart section was deposited either 8.1–8.0 Ma (C4An.2n) or 8.3–8.2 Ma (C4Ar.1n chron) ago. The Tihany Formation was deposited in a variety of palaeoenvironments related to deltas entering Lake Pannon. It is built up of parasequences, i.e. shallowing up successions from below wave base to lake level generated by sediment accumulation. Parasequences were formed on the delta front or in inter-distributary bays to delta-plain swamps and distributary channels. Beyond the high frequency lake-level and partly autocyclic environmental fluctuations, most likely climatically induced fourth-order lake-level changes of about 15–30 m amplitude occurred, resulting in minor transgressions followed by repeated progradation of deltaic lobes. Although the Tihany (as well as the very alike Somló) Formation is found along the rim of the hills currently, during its origin it was deposited in the same way as the Újfalu Formation known only from the subsurface of deep basins. The dynamics of deltaic settings feeding to Lake Pannon can be understood by studying the Tihany Formation in outcrops. The only difference among the two formations might be in the number of overlying delta cycles and their thickness. Both numbers were determined by rate of subsidence smaller at basement highs where Tihany Formation accumulated than at basin areas where Újfalu Formation was definied. It is suggested here to include Tihany (and Somló) beds as members of the Újfalu Formation. Fourth-order sequence boundaries were recognized between the overlying progradational deltaic bodies. In the vicinity of Tihany no evidences of lake-level drops were revealed, but elsewhere small incised-valley fills point to minor lake-level drops. Overall regression interrupted by transgressive events continued on the study area until the shelf edge of Lake Pannon shifted as far to the south as 50-60 km, i.e. at about 8 Ma ago. Since then flooding events became rare and small in amplitude, then the area became a terrestrial plain. Fluvial deposits are not known from the direct vicinity, but travertines formed in small freshwater ponds fed by karst springs. The transition from lacustrine to terrestrial palaeoenvironments is part of the overall normal regression as a result of high sediment input to Lake Pannon. Large incised valleys or other evidences of recurring terrestrial conditions which could be related to third-order sequence boundaries mappable all over the Pannonian Basin were identified neither in Tihany nor in Újfalu Formations

Double-difference relocation of the 29 January 2011 ML 4.5 Oroszlány earthquake and its aftershocks and its relevance to the rheology of the lithosphere and geothermal prospectivity

In the central part of Hungary, an earthquake with the local magnitude of 4.5 occurred near the town of Oroszlány, on 29 January 2011. The main shock and its more than 200 aftershocks were recorded by a significant number of three-component seismic stations, which enabled us to perform multiple event location on the event cluster. We applied the double difference, HypoDD method to relocate the aftershock sequence in order to identify the pattern of active faulting. We used the extended International Seismological Centre location algorithm, iLoc to determine the initial single event locations for the aftershock sequence and applied multiple event location algorithm on the new hypocenters. To improve both location precision and accuracy, we added differential times from waveform cross correlation to the double-difference multiple event location process to increase the accuracy of arrival time readings. We show that both HypoDD collapses the initial, rather diffuse locations into a smaller cluster and the vertical cross-sections show sharp images of seismicity. Some of the relocated events in the cluster are ground truth quality with a location accuracy of 5 km or better. Having achieved accurate locations, we further examined the extent of the seismogenic zone. We investigated the relationship between geothermics and seismicity through strength profiles constructed for the study area. The aftershocks of the Oroszlány earthquake are dominantly in the range of 5–10 km, fitting well to the extent of the thin brittle part of the crust. It shows that the events are well in accordance with a thermally attenuated lithosphere and elevated geothermal gradient in the upper crust and basin sediments. These findings underline the geothermal prospectivity of the Panonian Basin. © 2017, Akadémiai Kiadó

The assessment of neural injury following open heart surgery by physiological tremor analysis

INTRODUCTION: The appearance of post-operative cognitive dysfunction as a result of open heart surgery has been proven by several studies. Focal and/or sporadic neuron damage emerging in the central nervous system may not only appear as cognitive dysfunction, but might strongly influence features of physiological tremor. MATERIAL AND METHODS: We investigated 110 patients (age: 34-73 years; 76 male, 34 female; 51 coronary artery bypass grafting (CABG), 25 valve replacement, 25 combined open heart surgery, 9 off-pump CABG) before surgery and after open-heart surgery on the 3(rd) to 5(th) post-operative day. The assessment of the physiological tremor analysis was performed with our newly developed equipment based on the Analog Devices ADXL 320 JPC integrated accelerometer chip. Recordings were stored on a PC and spectral analysis was performed by fast Fourier transformation (FFT). We compared power integrals in the 1-4 Hz, 4-8 Hz and 8-12 Hz frequency ranges and these were statistically assessed by the Wilcoxon rank correlation test. RESULTS: We found significant changes in the power spectrum of physiological tremor. The spectrum in the 8-12 Hz range (neuronal oscillation) decreased and a shift was recognised to the lower spectrum (p < 0.01). The magnitude of the shift was not significantly higher for females than for males (p < 0.157). We found no significant difference between the shift and the cross-clamp or perfusion time (p < 0.6450). CONCLUSIONS: The assessment of physiological tremor by means of our novel, feasible method may provide a deeper insight into the mechanism of central nervous system damage associated with open heart surgery

Az autochtonitás hatása az Alföld honfoglalás kori (10. századi) népességére

The present paper deals with the 10th century population history of the Hungarian Great Plain. Our attention was primarily focused on the proportion of the 10th century Hungarian conquerors and the local populations. As the craniological results showed, the percentage of the local population might have been 57%, while that of the immigrants might have presented a smaller ratio (43%). The components of the local population were also estimated back to the previous one thousand years. According to these examinations, the characteristic features of the population surviving in the Great Plain were mainly suggestive of the Sarmatian and Germanic eras. The immigrants of the Late Avar period preceding the age of the Hungarian conquest did not seem to have been of the same importance

The role of pargasitic amphibole in the formation of major geophysical discontinuities in the shallow upper mantle

Several explanations have been proposed for variation in geophysical properties and depths to the lithosphere-asthenosphere boundary (LAB) and mid-lithospheric discontinuities (MLD). Here we investigate the proposal that the dehydration solidus of pargasitic amphibole-bearing upper mantle with very low bulk water (hundreds ppm) may be one of the main reasons for the observed geophysical anomalies. The pargasite dehydration solidus may be associated with a very small degree of partial melting in the upper mantle at temperatures and pressures in excess of 1050 °C (for geochemically more depleted) or 1100 °C (for geochemically more fertile upper mantle) and from 1 to 3 GPa (~ 30 to 90 km) respectively. This small amount of partial melt may be responsible for changes in geophysical properties (e.g. lower seismic velocity, higher attenuation of seismic waves, higher electrical conductivity) in association with the LAB and MLD. This simple petrologic model is tested on the abundant geophysical data of the Carpathian-Pannonian region (CPR), central Europe. The high resolution heat flow data available in the CPR allows us to estimate the depths to intersection of area specific depth-temperature curves with the dehydration solidus temperatures (1050 and 1100 °C isotherms). There is relatively small mismatch (< 5 km) between the position of these intersections and the geophysically determined LAB in the central area of the CPR. These observations lend support for the proposition that the dehydration solidus may be largely responsible for depth variation of the LAB in young continental rift areas. Towards the margins of the CPR, however, where the heat flow is lower (< ~ 70 mW/m2), the predictive capability of the dehydration solidus model deteriorates. This is because, for lower geothermal gradients, pargasitic amphibole breaks down at ~90 km (or ~ 3 GPa) before temperature exceeds the dehydration solidus temperatures. Consequently we should expect changes in geophysical properties attributable to hydrous silicate melt at ~90 km depth in areas where surface heat flow is lower (i.e. Precambrian cratonic shields, Phanerozoic continental lithospheres or, possibly older oceanic plates). Alternatively, in these areas, the intersection of the geotherm with pargasite breakdown may correlate with the MLD rather than the LAB, which is at deeper levels. A global review is also included to assess whether: 1) the position of the dehydration solidus temperatures in the upper mantle (~1050 and 1100 °C isotherms) could explain the origin of the LAB under younger oceanic plates with higher surface heat flow; 2) there is indeed global anomalies at ~90 km depth, which are often interpreted as MLDs, in older continental areas, older oceanic crust and cratons with lower surface heat flow