Terrestrial heat flow in Hungary

Summary The geothermal gradient in the Carpathian Basin lies between 40–70 C/km. According to careful measurements in shafts the value of terrestrial heat flow in the southern part of Hungary is (2.055–3.066)·10^–6 cal/cm² sec. These measurements are believed the first ever attempted in continental Europe. Systematic heat flow measurement are being extended to other part of this country.     

Terrestrial heat flow in Hungarian Permian strata

Summary Latest measurements of terrestrial heat flow in the Hungarian and Russian parts of the Carpathian basin confirm previously measured high flow values between 2.0–3.3 cal/cm² sec. Recent measurement in the Permian anticline structure of the Mecseck. Mts. in Hungary gave 2.4 cal/cm²sec, whereas in the Russian part of the basin, near to the Hungarian border 2.6 cal/cm² sec was measured in Miocene sediments. For more than 100000 km² surface of the Carpathian basin covered by Hungary and parts of Slovakia and Russian the high heat flow is an established fact.     

Imbrication, flow direction and possible source areas of the pumice-flow tuffs near Bend, Oregon, U.S.A.

Imbrication, indicating flow and source direction, occurs in three Pleistocene or upper Pliocene pumice-flow tuffs exposed in a 700-km² area on the east flank of the Cascade Range near Bend, Oregon, and shows the location of previously unknown source vents of these tuffs. The imbrication is formed by inclined elongate and/or flat pumice or lithic fragments and locally by elongate plagioclase crystals. Imbrication is best developed within the lower zones of individual flow units; the pumiceous top zones also locally show imbrication directions parallel to that in the lower zones. Moreover, the areal pattern of size distribution of lithic and pumice fragments in the flows is concordant with the flow direction pattern indicated by imbrication.The upper pumice flow shows a fan-shaped pattern of flow directions indicated by imbrication which points to a western source. A possible vent, about 20 km west of Bend in the highland near Broken Top Volcano, is marked by many silicic domes and basaltic cinder cones where there is a 6–8 mgal negative Bouguer gravity anomaly. In contrast, imbrication in the middle and lower pumice flows indicates flow from a source southwest of Bend. Vents in this direction are not obvious. Possible buried vents are located about 30 km and 45 km southwest of Bend near Sitkum Butte and Lookout Mountain, respectively.     

Active deformation in the Vrancea region,Rumania

Recent and historical seismicity as well as reliable fault plane solutions are used to study the active deformation caused by the occurrence of intermediate depth (60–170 km) earthquakes of the Vrancea region, Rumania. In this area, located in the southeastern part of the Carpathian arc, the westward subduction of the Carpathian trench has terminated, leaving continental lithosphere, at present, at the arc. The principalT axis of the intermediate depth events trends N159°E and has a plunge of 74°, which is the same as the dip of the subducted plate. TheP axis has a trend of 314° and a shallow plunge of 15°. The analysis of the moment tensor of six focal mechanisms showed that the dominant mode of deformation of the subducted lithosphere is a down-dip extension at a rate of about 2 cm/yr, based on seismicity data.     

OSL dating of loess deposits bracketing Sheep Creek tephra beds,northwest Canada: Dim and problematic single-grain OSL characteristics and their effect on multi-grain age estimates

Geochemically-fingerprinted tephra beds provide unique chronostratigraphic markers for comparing Quaternary sedimentary records across eastern Beringia (Alaska and Yukon Territory). Establishing reliable numerical age control on these tephra horizons enables them to be placed within firm temporal frameworks and increases their potential as correlative tools for regional palaeoenvironmental reconstructions. To this end we present new single-grain and multi-grain quartz optically stimulated luminescence (OSL) chronologies for loess deposits bracketing three well-documented and regionally significant variants of the Sheep Creek tephra (SCt) at two sites in west-central Yukon Territory (Ash Bend and Quartz Creek). Single-grain OSL ages bracketing the SCt-A and SCt-K reveal that these tephras were deposited during late Marine Isotope Stage (MIS) 5 or early MIS 4. The SCt-C variant and associated organic-rich bed at Ash Bend were likely deposited during late MIS 5, based on a single-grain OSL age of ∼81 ka for the overlying sediments. The single-grain OSL ages obtained for these deposits are in stratigraphic order and in broad agreement with a fission track age estimate of ∼77 ka for the SCt-K. In contrast, comparative chronologies obtained using multi-grain aliquots are stratigraphically inconsistent and unexpectedly young when compared with the independent SCt-K age. Detailed examination of the single-grain OSL datasets reveal a range of unfavourable luminescent properties that could have contributed to the multi-grain aliquot age discrepancies; including, very low yields of luminescent grains, weak OSL signal sensitivities and large populations of aberrant grains (particularly 0 Gy grains and ‘dim’ grains with a tendency to sensitise during the equivalent dose (D_e) measurement sequence) that have similarly sized OSL signals as grains used for D_e analysis. Synthetic aliquot D_e datasets constructed from single-grain OSL measurements reveal that the large proportional light sum contributions of 0 Gy and dim grains could possibly account for multi-grain age underestimations in some of the Ash Bend samples. In light of these potentially problematic averaging effects, we do not consider the multi-grain OSL ages to be reliable and suggest that single-grain approaches may be preferable for dating sediments with similar quartz luminescence behaviours across this region.     

First macroseismic map with geological background (composed by L.H. Jeitteles)

The little-known work by Ludwig Heinrich Jeitteles (1830–1883) on the 1858 Žilina strong earthquake in the Carpathian Mountains is commemorated and analysed. Besides his detailed macroseismic analysis of the earthquake — including the construction of isoseismal lines according to local macroseismic reports — Jeitteles was the first to superimpose the macroseismic field over a generalized geological map, which enabled him to describe the earthquake effects in relation to the geological structure of the affected region. These achievements allow us to acknowledge L.H. Jeitteles as one of founding fathers of seismological research of midnineteen century.     

Seismic Wave Velocities in Deep Sediments in Poland: Borehole and Refraction Data Compilation

Sedimentary cover has significant influence on seismic wave travel times and knowing its structure is of great importance for studying deeper structures of the Earth. Seismic tomography is one of the methods that require good knowledge of seismic velocities in sediments and unfortunately by itself cannot provide detailed information about distribution of seismic velocities in sedimentary cover. This paper presents results of P-wave velocity analysis in the old Paleozoic sediments in area of Polish Lowland, Folded Area, and all sediments in complicated area of the Carpathian Mountains in Poland. Due to location on conjunction of three major tectonic units — the Precambrian East European Craton, the Paleozoic Platform of Central and Western Europe, and the Alpine orogen represented by the Carpathian Mountains the maximum depth of these sediments reaches up to 25 000 m in the Carpathian Mountains. Seismic velocities based on 492 deep boreholes with vertical seismic profiling and a total of 741 vertical seismic profiles taken from 29 seismic refraction profiles are analyzed separately for 14 geologically different units. For each unit, velocity versus depth relations are approximated by second or third order polynomials.     

The velocity structure of the Carpathian zone from the ambient noise surface wave tomography

The dispersion curves of the Rayleigh wave group velocities are constructed along 60 interstation seismic paths in Central Europe based on the cross-correlation function of seismic noise. Together with the previous data (Yanovskaya and Lyskova, 2013), this information was used for reconstructing the three-dimensional distribution of S-wave velocities in the upper mantle of the Carpathian region. In the present work, the previous results are refined by expanding the data set by the additional seismic paths that intersect the Carpathian region and by modifying the procedure for constructing the locally averaged dispersion curves so as to obtain a more compact resolution. The results of the study suggest the complex, multidirectional character of the plate motion in the region.     

A note on the microseismic noise in the western carpathians

Summary The level of microseismic noise is studied at locations in the Western Carpathians where, apart from the vertical component of the noise, also its horizontal component was recorded by a broad-band seismograph. The amplitudes of the permanent noise in the horizontal component ranged from 10 to 83 nm and, at most locations, the predominant periods T>0.45 s, although the predominant periods of the vertical component in the Carpathian region are mostly within the interval T 0.24–0.37 s.     

Modelling of the conductance distribution at the eastern margin of the European Hercynides

Magnetic variation data recorded at 143 sites in the period range of 1000–6000 seconds were used to model the conductance distribution in the eastern part of the Bohemian Massif (BM) and the West Carpathians (WCP). The region represents a contact zone of the Palaeozoic Hercynian and Tertiary Carpathian orogenic systems. Two anomalies in the distribution of the electrical conductivity were found. One with a simple two-dimensional feature is located approximately near the boundary of the Inner and Outer West Carpathians, but the other of a complicated three-dimensional character is at the eastern margin of the BM. We inverted the observed geomagnetic data for the conductance in a unimodal thin sheet embedded at a specific depth. The inversion algorithm minimises the parametric functional that sums the squared norm of the misfit and the stabilising functional, and employs conjugate gradient optimisation. To express the sharp tectonic boundaries, we employed a minimum gradient support functional, which is applied in areas with strong variations of the model parameters. The inversion results confirmed a quasi-linear character of the regional anomaly distinguishing the Carpathian plate and led to new insight into the anomaly over the eastern margin of the BM. According to the results of the modelling the anomaly is formed by several conductive belts intersecting the anomalous zone. These belts follow important faults, dividing the transition zone between the BM and the WCP into individual blocks.     

Environmental change,hydromorphological reference conditions and the restoration of Polish Carpathian rivers

In the twentieth century Polish Carpathian rivers were considerably modified by channelization and gravel mining, with significant detrimental effects to their ecological integrity, vertical stability of the streambeds and flood hazard to downstream river reaches. Restoration of the rivers is thus necessary to improve their ecological status and re‐establish geomorphic dynamic equilibrium conditions. Various approaches to defining hydromorphological reference conditions, proposed to date in river restoration literature, have serious deficiencies. In particular, environmental changes that took place in the catchments of Carpathian rivers during the twentieth century invalidate the historical state of the rivers as reference for their restoration. This is illustrated by a change from bar‐braided to island‐braided channel pattern that occurred in the past century in unmanaged sections of the Czarny Dunajec in response to a reduction in flow and sediment dynamics of the river. We indicate that reference conditions should be defined as those which exist or would exist under present environmental conditions in the catchment but without human influence on the channel, riparian zone and floodplain of the river which is to be restored. This assumption was tested through the evaluation of hydromorphological river quality of the Czarny Dunajec according to the European Standard EN‐14614. The evaluation confirmed a high‐status hydromorphological quality in an unmanaged channel section, which can thus be used as a reference for restoration of impacted river sections. Copyright © 2012 John Wiley & Sons, Ltd.     

Channel sediment variability along a river: A case study of the Siret River (Romania)

The Siret River has the largest drainage basin (42 274 km²) in Romania. It gathers all the rivers from the eastern part of the Eastern Carpathians, a fact that causes marked asymmetry of the basin. This study is principally concerned with changes in the form of the longitudinal profile and the grain size variability introduced by the Carpathian tributaries. Channel sediment analyses considered the petrography, granulometry, and morphometry of the pebbles, relating these to the river bed and floodplain geometry and to some properties of the drainage basin. The following conclusions arise. The Siret River undergoes an intense regrading of its longitudinal profile, with marked aggradation between transects 24 and 26 (see Figures 1 and 2). This reflects selective accumulation of coarse material due to the massive contribution of the Carpathian tributaries. This phenomenon has been continuous throughout the Holocene, resulting in the gravel sheet formation of the Pericarpathian piedmont.     

Bankfull discharge in mountain streams: theory and practice

The results are presented of an investigation of bankfull discharge in two Polish Carpathian streams: Skawica and Krzyworzeka. Existing definitions of river bankfull were reviewed and applied in tests carried out on selected cross‐sections of the streams. The Woodyer method was given special attention, with a correspondingly detailed survey of plants characterizing river benches. Riley's bench index method and the methods of Williams, Wolman, Schumm and Brown, and Woloszyn were tested. The report concludes that bankfull discharge value for a mountain stream should not be reported as a single number, but rather as a range of discharges within which one could expect the bankfull value to lie. Copyright © 2002 John Wiley & Sons, Ltd.     

Spinel peridotite xenoliths in the West Carpathian late cenozoic alkali basalts and their tectonic significance

In the Late Cenozoic West Carpatian alkali olivine basalts spinel peridotite xenoliths have been found. Their mineral composition corresponds to those found in this type of xenoliths in alkali basalts throughout the world (Mg-rich olivine, Cr-diopside, clinopyroxene, spinel). For the studied West Carpathian alkali olivine basalts kaersutite amphibole and clinopyroxene magacrysts are characteristic. The presence of the xenoliths under consideration in the boundary zone between Tatra and Pannonian blocks is the consequence of tectonic conditions (thickness of the Crust) in the area mentioned as distinct from the other West Carpathian areas of alkali olivine basalt occurrences.     

Observations of Alfvén Ionospheric Resonances on the Earth's Surface

The paper briefly reviews the preliminary results of observations of Alfvén ionospheric resonances performed in the northern Carpathian Mountains (south-eastern Poland) by the Cracow Schumann Resonances Group. The results confirm the simple models proposed recently by Lysak and Sentman.     

Multifractal and Chaotic Analysis of Vrancea (Romania) Intermediate-depth Earthquakes: Investigation of the Temporal Distribution of Events

The Vrancea seismic region contains an isolated cluster of events beneath the Carpathian Arc Bend in Romania, dipping to about 200 km depth. Seismic activity mainly occurs at intermediate depths (h > 60 km). The main goal of the paper is to perform an in-depth, complex analysis of the occurrence times of these intermediate-depth events. We also try to show the versatility of the methods used to characterize different aspects of the seismicity evolution and to offer a user-friendly software toolbox to do most of the related computations. The earthquake catalog used in this study spans from 1974 to 2002 and includes only the intermediate-depth events. In the first part of the paper, we analyze the multifractal characteristics of the temporal distribution of earthquakes. The study reveals two distinct scaling regimes. At small scales we found a clear nonhomogeneous, multifractal pattern, while at large scales the temporal distribution of events shows a monofractal, and close to Poissonian (random), behavior. The multifractal behavior at small scales (minutes-hours) is shown to be clearly an effect of the short aftershock sequences that occurred after some major Vrancea earthquakes. In the second part of the paper we analyze whether our temporal series shows a persistent (or anti-persistent) long-term behavior, by using the Detrended Fluctuation Analysis (DFA) method. The results suggest that the analyzed temporal series of Vrancea earthquakes is a non-correlated process. In part three of the paper we seek to determine whether the dynamics of our earthquake system (described by the occurrence time of Vrancea earthquakes) is deterministically chaotic, deriving from a rather simple evolution law, or whether it is stochastic and is generated by a system that possesses many degrees of freedom. The results suggest that our signal is stochastic (probably does not possess an attractor). The limited time-span of the catalog and the analysis performed in this paper cannot rule out the emergence of an interesting, quasi-deterministic and low-dimensional structure in the case of major Vrancea earthquakes.Acknowledgement One of the authors (BE) is grateful to the Japanese Ministry of Education for providing him a Monbusho scholarship for studying in DPRI, Kyoto University. We thank Z.R. Struzik, M Holschneider, J. Mori and D. Kaplan for their useful comments, and acknowledge the support of the staff of DPRI, Kyoto University and the National Inst. for Earth Physics, Bucharest. We thank the two reviewers, M.B. Geilikman and M. Anghel, for their useful suggestions which improved the quality of this work.     

Preliminary analysis of the connection between ocean dynamics and the noise of gravity tide observed at the Sopronbánfalva Geodynamical Observatory,Hungary

An experimental development of a computer controlled photoelectric ocular system applied for the LaCoste and Romberg G949 gravimeter made the continuous observation of time variation of gravity possible. The system was operated for half a year in the Sopronbánfalva Geodynamical Observatory to test its capabilities. The primary aim of this development was to provide an alternative and self-manageable solution instead of the standard electronic (Capacitive Position Indicator) reading of this type of gravimeter and use it for the monitoring of Earth tide. It, however, turned out that this system is sensitive enough to observe the effect of variable seismic noise (microseisms) due to the changes of ocean weather in the North Atlantic and North Sea regions at microGal level (1 μGal = 10⁻⁸ m/s²). Up to now not much attention was paid to its influence on the quality and accuracy of gravity observations because of the large distance (>1000 km) between the observation place (generally the Carpathian–Pannonian basin) and the locations (centres of storm zones of the northern hydrosphere) of triggering events. Based on an elementary harmonic surface deformation model the noise level of gravity observations was compared to the spectral characteristics of seismic time series recorded at the same time in the observatory. Although the sampling rate of gravity records was 120 s the daily variation of gravity noise level showed significant correlation with the variation of spectral amplitude distribution of the analysed high pass filtered (cut-off frequency = 0.005 Hz) seismograms up to 10 Hz. Also available daily maps of ocean weather parameters were used to support both the correlation analysis and the parameterization of the triggering events of microseisms for further statistical investigations. These maps, which were processed by standard image processing algorithms, provide numerical data about geometrical (distance and azimuth of the storm centres relative to the observation point) and physical (mass of swelling water) quantities. The information can be applied for characterizing the state of ocean weather at a given day which may help the prediction of its influence on gravity measurements in the future. Probably it is the first attempt to analyse quantitatively the effect of ocean weather on gravity observations in this specific area of the Carpathian–Pannonian region.     

Imaging Pn velocities beneath the Pannonian basin

The Pannonian depression is an extensional back-arc basin in central Europe and is an integral part of the Alpine–Carpathian orogenic mountain belts. It can be characterized by thinned lower crust, shallow Moho discontinuity, high surface heat flow and Moho temperature, implying recent active tectonic processes. Imaging the velocity structure of the upper mantle may help us to better understand the structure and formation of the Pannonian region.In this paper, P_n traveltimes from regional earthquakes are used to tomographically image the lateral velocity variations in the uppermost mantle beneath the Pannonian basin. The set of linear tomographic equations, built up of the time term equation for each source–receiver pair, is solved by a truncated singular value decomposition algorithm. The explicit computation of the generalized inverse of the tomographic equations makes it possible to deduce both the resolution matrix and the model covariance matrix, allowing us to estimate the resolution and reliability of the solution.The mean compressional wave velocity in the uppermost mantle beneath the Pannonian basin is 7.9 km/s, substantially lower than the average continental P_n velocity of 8.1 km/s. It is mostly due to the high Moho temperature having values on average 400–500 °C more than those in the surrounding areas. The velocity anomalies range from −0.3 to 0.3 km/s relative to the mean velocity of 7.9 km/s. Due to high Moho temperature, below the North Hungarian range low (7.6–7.7 km/s) velocities can be found. High-velocity anomalies of around 8.1 km/s can be detected along the W-SW boundaries of Hungary and at the junction of the Pannonian basin and the Southern Carpathians. The Great Hungarian Plain shows average (7.9 km/s) P_n velocities.     

Quaternary vertical movements of the earth's surface in East-Central Europe

Fluvial terraces in mountain territories and granulometric cycles in fluvial sediment complexes show 300–400 m uplifts in mountain regions and about the same sized subsidences in major East-Central European basins during the Quaternary (−2.4 Ma). The vertical movements are not at all regular and equal in the mountains nor in the great basins. The number of the terraces is different in the valleys and their mutual proportions also differ. Similarly, some local Quaternary basins were developed deeper in the peripheries of the large basins while the central parts are shallow. There are also some stable blocks between the mountains and the lowlands, which did not move essentially during the last two and a half million years.The course and velocity of Pliocene and Quaternary subsidence were proved in a local sub-basin of the Carpathian mountain arch by paleomagnetic measurements of cores from two deep boreholes. In the Körös Basin, filled with fine-grained fluvial sediment, the sedimentation rate was 0.16–0.19 mm/y in the last 700.000 years; 0.15–0.16 mm/y during the proceding one million years; and 0.22–0.28 mm/y during the Pliocene (from −5.2 to −2.4 Ma).In sub-basins filled with coarse-grained sediments, the sedimentation rate was 0.3–0.4 mm/y during the Quaternary.