Southeastern Carpathians Research Articles

Seismic Moments of Intermediate‐Depth Earthquakes Beneath the Hindu Kush: Active Stretching of a Blob of Sinking Thickened Mantle Lithosphere?

AbstractIntermediate‐depth seismicity beneath the Hindu Kush may reveal the Earth's best example of a stretching blob of mantle lithosphere sinking through the asthenosphere. Seismically, this region is the Earth's most active at intermediate depths (70–300 km). Fault plane solutions show nearly vertical stretching of the region in which the earthquakes occur, and a summation of seismic moment tensors implies that on average material at a depth of 300 km moves downward at ~40 mm/year relative to the overlying crust. As shown by Kufner et al. (2017, https://doi.org/10.1016/j.epsl.2016.12.043) and Zhan and Kanamori (2016, https://doi.org/10.1002/2016GL069603), the central part of the zone stretches so rapidly that this rate there is ~100 mm/year, much faster than the present‐day convergence rate of ~15 mm/year at the surface and across the Hindu Kush. The pattern of stretching, with maximum strain rates in the middle depths of the intermediate‐depth range, resembles that beneath the southeastern Carpathians, where Lorinczi and Houseman (2009, https://doi.org/10.1016/j.tecto.2008.05.024) have shown that seismicity is consistent with a blob of mantle lithosphere stretching rapidly and sinking into the asthenosphere, though more slowly than occurs beneath the Hindu Kush.

On the determination of fault plane solutions of weak crustal earthquakes of Vrancea region (Romania)

An inversion scheme using only few good quality high-frequency local waveforms was previously applied to estimate the source mechanism for a pilot set of crustal earthquakes with local magnitudes less than 4, from the bend of the South-eastern Carpathians. Taking advantage of the improved velocity and attenuation models recently determined for the study region, we reevaluate the focal mechanism of a couple of low-magnitude events (local magnitude ≥ 3), and assess the uncertainty of the fault plane solutions. The results evidence the increased reliability of the retrieved mechanisms and emphasize the capability of the approach to provide satisfactorily constrained fault plane solutions for the weak-to-moderate earthquakes in the study region.

Effects of latitudinal and elevational gradients exceed the effects of between-cytotype differences in eco-physiological leaf traits in diploid and triploid Hieracium alpinum

Polyploidy may affect a species’ eco-physiology, which might, in turn, trigger a shift in the distribution of its cytotypes. The arcto-alpine Hieracium alpinum (Asteraceae) encompasses two geographically allopatric cytotypes: diploids occurring in the South-Eastern Carpathians and triploids occupying the remaining, much larger part of the species range. We ask whether the natural populations of these two cytotypes, growing under partially different biotic and abiotic conditions, also differ in selected eco-physiological traits. To answer this question, we analyzed specific leaf area, foliar carbon (C) and nitrogen (N) contents, and their stable isotope compositions in plants sampled in 27 populations across the species range. Our results did not show any differences in these traits, except foliar N content being significantly higher in diploids. This pattern was mostly driven by the Scandinavian triploid populations exposed to significantly lower amounts of solar radiation and precipitation during the growing season when compared to the continental populations. As a consequence, in addition to lower foliar N content, the Scandinavian populations exhibited also lower foliar C content, but higher C/N ratios than continental populations regardless of their cytotype. Across the species range, foliar N and C contents were positively associated with the amount of precipitation, whilst δ15N was positively associated with temperature and negatively with the surrounding species richness and vegetation cover. Significantly lower values of δ13C in Scandinavian populations are likely the effect of increased atmospheric pressure due to the lower elevational position of Scandinavian sites. Reproductive output was positively linked to amounts of foliar nitrogen and δ15N. Our data thus show that (1) the latitudinal-driven abiotic and biotic factors affected eco-physiological traits in significantly larger extent than ploidy level and that (2) continental and Scandinavian populations, though all confined to the alpine belt, considerably differ in their eco-physiology likely reflecting different adaptation strategies.

Active tectonic deformation and associated earthquakes: a case study—South West Carpathians Bend zone

Active tectonic deformation is continuously shaping the landscape in the Alpine Orogenic system. Earthquakes are clear proves of neotectonic deformation process. In the Romanian Carpathians the most active deformation is recorded in the South Eastern Carpathian Bend Zone. Nevertheless, seismicity associated to latest orogenic stage of active deformation is not limited to this area. Other seismic regions, like the South West Carpathians Bend Zone, were identified. Recently, several earthquake sequences were recorded in the Caransebes-Mehadia (CMB) and Hateg basins (HB). These sedimentary basins developed over the South Carpathians, Getic/Supra Getic and Danubian basement napes, their evolution being related with the N-ward tectonic transport of the Carpathian Orogen, in the current position, during the Paleogene-Quaternary times. The aim of the present study is to perform a thorough analysis of the earthquakes recorded in these two basins in correlation with the observed geological structure to better understand and constrain the neotectonic processes affecting the SW Carpathians Bend Zone. The focal mechanisms determined for HB show a predominant strike-slip faulting component with the principal axes oriented approximately NW–SE (compression) and NE–SW (extension), a reorientation from the N-S one described for the Pliocene–Pleistocene phase. The focal mechanisms in CMB imply N–S extension with normal or strike-slip faulting. We argue that the present day tectonic processes are not restricted to the SE Carpathians Bend zone, as previously inferred. Instead they affect a much larger area of the Carpathian Orogen, like the SW Carpathians Bend zone.

Phylogeography, genetic structure and wing pattern variation of Erebia pronoe (Esper, 1780) (Lepidoptera: Nymphalidae) in Europe.

The distribution of genetic diversity within Erebia pronoe (Esper, 1780) populations in relation to biogeographic ranges is essential for understanding the processes of evolution, speciation and phylogeography in this species. A certain degree of genetic variability was expected because of the species' linkage solely to calcareous soils. These ideas were focused on the water ringlet E. pronoe, a European endemic montane butterfly distributed over a narrow area of mountains, with its occurrence dependent on nutrient plants. Therefore, the origin, occurrence, phylogeography and variability are described in defined mountain localities in Europe in the light of glaciation events that occurred during the Quaternary (Pleistocene) period. The species' phylogeography is based on a combination of two mitochondrial genes (COI, CR) and morphology (wing morphometry). The study comprised samples from the Western Carpathians, Pyrenees, Alps, South-Eastern Carpathians (Romania) and Southern Limestone Alps (Slovenia). Moreover, the species' remarkable phylogeographic structure was observed, including four morphologic lineages and divergent genetic lineages. These lineages cover the Carpathian Mountains as well as the Western European mountains (Spanish populations) with no apparent gene flow between most regions, even across distances of only hundreds of kilometres.

Cirsium greimleri

The newly described diploid species Cirsium greimleri (2n = 34; 2C = 1929.1‘60.6 Mbp) belongs to Cirsium sect. Cirsium and is distributed sparsely throughout the Eastern Alps and Dinarides, whereas the closely related tetraploid vicarious species C. waldsteinii (2n = 68; 2C = 3682.3‘69.8 Mbp) is endemic to the south-eastern Carpathians. The ploidy, genetic and morphological separation of both taxa is confirmed using flow cytometry, AFLP and morphometric analyses of 169 plants from 27 populations covering representatively distribution ranges of the respective species. The species differ in flower colour, with those of C. greimleri ruby red to brownish-purple and those of C. waldsteinii pinkish-purple to purple. The colour difference remains consistent when both species are cultivated together under the same conditions. Differences between the species in the size of the stomata, achenes, corollas, styles and pappus are statistically significant and congruent with differences in the ploidy level. Because both species are gynodioecious (their populations contain female and hermaphrodite plants), the generative features should be compared carefully with respect to gender (e.g. females with females) because the between-gender differences within the same species could be larger than the between-species differences. The basal and median cauline leaves of C. waldsteinii are narrower and more deeply lobed than those of C. greimleri. A slight difference in the flowering period is detected when both species are cultivated together, with C. waldsteinii flowering two weeks earlier than C. greimleri. Both species share ecological/ habitat preferences for subalpine woodland tall-forb vegetation. While C. waldsteinii hybridizes extremely rarely with co-occurring diploid congeners, C. greimleri produce hybrids very often, which increase the risk of its extinction via genetic erosion.

Repeated Earthquakes in the Vrancea Subcrustal Source and Source Scaling

The Vrancea seismic nest, located at the South-Eastern Carpathians Arc bend, in Romania, is a well-confined cluster of seismicity at intermediate depth (60 – 180 km). During the last 100 years four major shocks were recorded in the lithosphere body descending almost vertically beneath the Vrancea region: 10 November 1940 (Mw 7.7, depth 150 km), 4 March 1977 (Mw 7.4, depth 94 km), 30 August 1986 (Mw 7.1, depth 131 km) and a double shock on 30 and 31 May 1990 (Mw 6.9, depth 91 km and Mw 6.4, depth 87 km, respectively). The probability of repeated earthquakes in the Vrancea seismogenic volume is relatively large taking into account the high density of foci. The purpose of the present paper is to investigate source parameters and clustering properties for the repetitive earthquakes (located close each other) recorded in the Vrancea seismogenic subcrustal region. To this aim, we selected a set of earthquakes as templates for different co-located groups of events covering the entire depth range of active seismicity. For the identified clusters of repetitive earthquakes, we applied spectral ratios technique and empirical Green’s function deconvolution, in order to constrain as much as possible source parameters. Seismicity patterns of repeated earthquakes in space, time and size are investigated in order to detect potential interconnections with larger events. Specific scaling properties are analyzed as well. The present analysis represents a first attempt to provide a strategy for detecting and monitoring possible interconnections between different nodes of seismic activity and their role in modelling tectonic processes responsible for generating the major earthquakes in the Vrancea subcrustal seismogenic source.

Source parameters of the earthquake sequence that occurred close to the BURAR array (Romania) between 24 June and 1 July 2011

The seismic activity recorded in the Eastern Carpathians is poor and scarce (a few hundreds of small-to-moderate earthquakes in the Romanian catalogue over the last century). The installation in 2002 of the high-performance Bucovina (BURAR) array in the Eastern Carpathians area contributed to a significant growth of the capacity to monitor local seismicity. As a consequence, the earthquake sequence occurred between 24 June and 1 July 2011 close to the BURAR array is the best seismic data set ever recorded for this area. The location of the events using all the available data provided by the real-time seismic network of the National Institute for Earth Physics shows a NE-SW alignment along the western edge of Avramesti - Suceava fault. This fault is crossing the Carpathian Foredeep underthrusting the foreland units to the orogeny area. The distribution of the first P-wave polarities is fitting the geometry of this fault, indicating predominant strike-slip faulting, with right-lateral movement. The compression axis oriented E-W is in agreement with the stress field characterizing the region. We applied spectral ratios and empirical Green’s function methods to estimate the source parameters (corner frequency, seismic moment, source duration, rise time) for the events with moment magnitudes higher than 2.5 recorded within this sequence. The results show a simple fracture model for the main shock of 24 June 2011 and a constant stress drop scaling. Source parameter scaling relationships fit well the results obtained for other regions along the South-Eastern Carpathians and those which are typical for intra-continental areas.

Quantitative modeling of the lithosphere dynamics, earthquakes and seismic hazard

Understanding of lithosphere dynamics, tectonic stress localization, earthquake occurrences, and seismic hazards has significantly advanced during the last decades. Meanwhile, despite the major advancements in geophysical sciences, yet we do not see a decline in earthquake disaster impacts and losses. Although earthquake disasters are mainly associated with significant vulnerability of society, comprehensive seismic hazards assessments and earthquake forecasting could contribute to preventive measures aimed to reduce impacts of earthquakes. Modeling of lithosphere dynamics and earthquake simulations coupled with a seismic hazard analysis can provide a better assessment of potential ground shaking due to earthquakes. Here we present a block-and-fault dynamics (BAFD) model, which simulates earthquakes due to lithosphere dynamics and allows for studying the influence of fault network properties and regional movements on seismic patterns. The model's performance is analyzed in terms of reproduction of basic features of the observed seismicity such as the frequency-magnitude relationship, clustering of earthquakes, occurrences of large events, fault slip rates, and earthquake mechanisms. Several studies related to the application of the BAFD model to the following earthquake-prone regions are reviewed: the southeastern Carpathians, Caucasus, the western India, Tibet-Himalaya, and the Sunda Arc. We examine then a new approach to seismic hazard analysis, which is based on instrumentally recorded, historical and BAFD-simulated earthquakes, and analyze how earthquake modeling can assist in hazard assessment. Finally, we discuss perspectives in modeling of earthquake occurrences and improvements in hazard assessment.

EMPIRICAL GREEN'S FUNCTION DECONVOLUTION APPLIED FOR VRANCEA EARTHQUAKES OCCURRED IN THE LAST TEN YEARS

The Vrancea seismogenic area, located at the South-Eastern Carpathians in Romania, is generating extreme destructive subcrustal earthquakes in Europe. The largest events generated in the last ten years in the Vrancea subcrustal domain occurred on May 14, 2005 (01:53, 45.64oN, 26.53oE, h=149 km, Mw = 5.5), April 25, 2009 (17:18, 45.68oN, 26.62oE, h=110 km, Mw = 5.4) and October 6, 2013 (01:37, 45.67oN, 26.58oE, h=135 km, Mw = 5.2). The purpose of the present paper is to determine the seismic source parameters of these events using the Empirical Green s function deconvolution and spectral ratios techniques. To this aim, we selected a set of empirical Green s functions in association with the three main events, as co-located events with similar focal mechanism. The large number of high-quality waveforms recorded for the main shock-EGF pairs provides a good database to constrain source parameters, even though the events are relatively small and are recorded practically in the far field. The seismic moment-source radius scaling and stress drop values range, match well the results as previously obtained on larger data sets.

Three climatic cycles recorded in a loess-palaeosol sequence at Semlac (Romania) – Implications for dust accumulation in south-eastern Europe

Recent inve\stigations of the Semlac loess section in the south-eastern Carpathian Basin, which is situated at an undercut slope position on the right bank of the Mures River in its lower reaches (Banat region, western Romanian), are presented and discussed. Dating back to marine isotope stage (MIS) 10, the more than 10 m thick loess sequence includes four fossil soil-complexes developed in homogenous and relatively fine silty loess. Because of the good preservation of the sediment, Semlac is regarded as a key section for the Carpathian Basin, which offers possibilities to a) improve the understanding of the type and composition (loess homogeneity and pedogenic alteration) of the lowland loess sequences in the Carpathian Basin also beyond the last interglacial palaoesol complex, b) to reconstruct the temporal evolution of the local loess-palaoesol successions, c) gain better insight into the regional paleoenvironments of the last 300ka and d) to compare the loess of the region to loess-sequences in adjacent areas and to dust proxy data in the northern hemisphere. An integrated age model based on correlation to reference records and luminescence dating is compiled. Applying this age model we compare climate proxy data from Semlac to both global data and to data from the very southeast of the Carpathian Basin (Vojvodina, Serbia). The obtained results provide new insight into the dust accumulation regime for the eastern Carpathian Basin and offer new palaeoenvironmental information for the region and are an important step towards establishing a catena from the thin loess-like sediments of the Banat foothills in the East towards the thicker and seemingly more complete loess sections of the south-eastern and central Carpathian Basin. Disentangling grain size data from soil formation proxies is used to investigate patterns of non-local dust. Patterns of non-pedogenetic fine material are similar to grain size proxies from China and other parts of the northern hemisphere, suggesting western and eastern Eurasian loess to have (at least partly) similar mechanistic/climatic origins. (C) 2016 Elsevier Ltd. All rights reserved.

Exploring the different facets of plant endemism in the South-Eastern Carpathians: a manifold approach for the determination of biotic elements, centres and areas of endemism

In the European Alpine System, the Carpathian Mountains are recognized as one of the major centres of diversity and endemism. In the present study, we aimed to explain the spatial structure of plant endemism in its South-Eastern subunit by the complementary use of diversity indices, parsimony analysis of endemicity (PAE), biotic element analysis (BEA), and barrier analysis. We analyzed the available information on 111 plant taxa confined to the South-Eastern Carpathians, mapped using two different sets of operational geographical units (OGUs): 71 geomorphological units and 64 quadrats. Our results showed that centres of endemics diversity largely corresponded to the areas of endemism and biotic elements. PAE consensus cladogram outlined four major areas of endemism (with three nested ones): (1) Danubian; (2) western part of the Southern Carpathians; (3) eastern part of the Southern Carpathians; and (4) Pocutico-Marmarossian. Out of the seven identified biotic elements, five were spatially clustered and overlapped the major areas of endemism, with one notable exception: the calcareous massifs from the Eastern Carpathians, not identified through PAE. Conversely, the latter outlined a nested area of endemism (Cozia – Buila-Vânturarița), omitted by BEA. Barrier analysis identified three major breaks in the distribution of endemics: (1) south of the Retezat – Țarcu – Godeanu mountain group; (2) north of the Piatra Craiului – Bucegi – Ciucaș mountain group; and (3) north of the Rodna massif. The results obtained in here using different methods are generally spatially convergent, indicating highly structured patterns of endemism in the South-Eastern Carpathians. These patterns mostly follow the present-day distribution of alpine habitats and calcareous bedrock, which might have acted as isolating factors through insularity. Interestingly, three of the spatial clusters of OGUs obtained from the endemics distribution analyses (the Eastern Carpathians, as well as eastern and western parts of the Southern Carpathians) largely also correspond to the mid-Miocene archipelago configuration of landmasses in this part of the Carpathians. This might suggest the existence of older migration barriers that emerged throughout the Neogene Period. Differences in the spatial patterns outlined by PAE and BEA could stem from partial sympatry of endemics caused by post-speciation processes such as dispersal or extinction. Additionally, sympatric distribution of taxa with disjunct populations may be caused by the absence of divergence among segregated populations, such as the patterns of relict distributions seen in alpine plants. Finally, the complementary use of these methods may prove to be an efficient approach for better understanding the geographical structure of endemism and provide a starting point for further testing of hypotheses on evolutionary processes.

The Crvenka loess-paleosol sequence (Vojvodina, Northern Serbia)- a record of continuous domination of the Late Pleistocene grasslands

In this study we present a comparison of two independent paleo-environmental evidences: novel n-alkane biomarkers and traditional land snails assemblages, associated with widely used proxy records such as the low field magnetic susceptibility, grain size and various isotopic and geochemical indices. These paleo-environmental proxy records provide evidence for the continued predominance of the different grassland vegetation types during the entire Late Pleistocene. The results presented in this study highlight the spatial differences in the environmental conditions during the Late Pleistocene across the European loess belt. Contrary to other European loess provinces characterized by high diversity of the Late Pleistocene environments (ranging from tundra-like to deciduous forest habitats), our investigations indicate a continued dominance of grassland-dominated ecosystems in the southeastern Carpathian Basin. This uninterrupted presence of Late Pleistocene grassland zone in the southeastern part of the Carpathian Basin may have played an important role in the preservation of exceptional biodiversity of the Balkan region, as well as in the migration of anatomically modern humans into Europe

Late Pleistocene climate evolution in Southeastern Europe recorded by soil bacterial membrane lipids in Serbian loess

Loess–paleosol sequences in the Vojvodina region in the southeastern Carpathian Basin have been intensively studied to obtain a high-resolution stratigraphical framework for the Upper Pleistocene in this part of Europe. In these studies, millennial-scale sedimentation variations in the Upper Pleniglacial have been coupled to the Greenland Ice dust record, indicating that the rapid climate variability characterizing the North Atlantic and Greenland areas, is reflected in the loess deposits at the southern edge of the European loess belt. Rapid variations were recently also reported for the stable isotopic composition of organic matter in the Surduk loess-paleosol sequence, located in the Vojvodina region, and were interpreted as episodes of increased C4-vegetation over the last glacial period. Based on potential coinciding changes in oceanic and atmospheric circulation patterns, these episodes were attributed to plant moisture stress rather than by fluctuations in temperature, although exclusive proof has not yet been provided. Here we report a high-resolution record of continental air temperature and precipitation over the past 40,000years based on soil bacterial lipid signatures preserved in the Surduk loess–paleosol sequence. Our temperature record shows a gradual warming trend, suggesting that moisture availability indeed seems to be the main factor driving the excursions to C4-vegetation around Surduk. We also find that continental air temperature changes in this region may be seasonally biased, and were driven by regional influences rather than by Northern Hemisphere climate forcings, likely as a result of the inland isolation of the Carpathian Basin by surrounding mountains. Support for a regional climate driver comes from comparison of our lipid-based temperature and precipitation records with similar records from the near-by Crvenka loess–paleosol sequence, which resemble the climatic trends recorded at Surduk.

Present or Absent? About a Threatened Fern, <i>Asplenium adulterinum</i> Milde, in South-Eastern Carpathians (Romania)

Asplenium adulterinum Milde is one of the rarest and most threatened representatives of the Aspleniaceae family in the Carpathians. Botanical literature mentioned the ladder spleenwort in many localities in South-Eastern Carpathians in the past, but during the last decades the species has not been collected and deposited in public herbaria by any botanist. All existing herbarium material in Romanian herbaria (including Asplenium trichomanes and A. trichomanes-ramosum) was revised and all available information from botanical literature was critically compiled in order to clarify the distribution of Asplenium adulterinum in the South-Eastern Carpathians. After almost 80 years since the first mention of the species in the Carpathians, this paper reports the recent identification of Asplenium adulterinum in three new locations in South-Eastern Carpathians (Ţesna Valley, Vânturătoarea Waterfall and Şugăului Gorges).

Present or Absent? About a Threatened Fern, <i>Asplenium adulterinum</i> Milde, in South-Eastern Carpathians (Romania)

Asplenium adulterinum Milde is one of the rarest and most threatened representatives of the Aspleniaceae family in the Carpathians. Botanical literature mentioned the ladder spleenwort in many localities in South-Eastern Carpathians in the past, but during the last decades the species has not been collected and deposited in public herbaria by any botanist. All existing herbarium material in Romanian herbaria (including Asplenium trichomanes and A. trichomanes-ramosum) was revised and all available information from botanical literature was critically compiled in order to clarify the distribution of Asplenium adulterinum in the South-Eastern Carpathians. After almost 80 years since the first mention of the species in the Carpathians, this paper reports the recent identification of Asplenium adulterinum in three new locations in South-Eastern Carpathians (Țesna Valley, Vânturătoarea Waterfall and Șugăului Gorges).

Modelling Runoff on a Small Lowland Catchment, Hungarian Great Plains

Abstract The lowland region of the South-Eastern Carpathian Basin faces extreme hydrological conditions, therefore the more detailed understanding, monitoring and predicting of the hydrological regime on catchments have high importance. However, in the region only few measured data are available in terms of evaporation, runoff, infiltration and water retention, and this is especially true concerning small catchments. In the meantime these areas support extensive agriculture, therefore more information is needed to manage future drying and irrigational demands. In the present research runoff and discharge were modelled for a ten year period and compared to at-a-station measurement data on the Fehértó-majsa Canal, a sub-catchment of the Tisza River, in order to test the predictability of hydrological changes related to future climate change. Modelling was made by applying a coupled MIKE SHE/MIKE 11 model and integrating all available topographic, pedologic, climatic, hydrologic and vegetation data. Consequently, another motivation of the research was to assess the suitability, data demand and limitations of the MIKE modelling environment on lowland catchments. As from all available data sources soil data seemed to be the least accurate, sensitivity tests were made by changing different soil parameter. Based on the results, the developed model is highly suitable for the estimation of annual and monthly runoff. Nevertheless, concerning daily data a general overestimation of discharge was experienced during low flow periods, and a time lag appeared between measured and modelled discharge peaks during high flow periods. In all, the results of the study can greatly support the realization of water management and planning projects in the drought prone sand land catchments where only a few directly measured data are available

Assessment of recent tectonic evolution and geomorphic response in SE Carpathians (Romania) using hypsometric analysis

The study investigates correlations between the recent tectonic evolution of the external South-Eastern Carpathians and the characteristics of the hypsometric curves, derived for various Horton-Strahler basin orders. The analysis focuses on an area of about 8000 km 2 , delineated by the Trotus Fault in the north, the southern limit of the Buzau River catchment, Brasov and Focsani Basins in the west, respectively, east, known to conserve the youngest topography in the Romanian Carpathians. Considering the effects of the Quaternary uplift, these limits include the less elevated region of Subcarpathians. Spatial distribution of the hypsometrical integrals (HI) values was evaluated taking into account basin order, main lithological features and distance from major structural lines as well as some local indices of spatial autocorrelation. The results show that HI reflects both the specificity of regional tectonic evolution and denudation. However this is better sustained for the higher order basins (>3).

Nature of the Vrancea seismic zone (Eastern Carpathians) – New constraints from dispersion of first-arriving P-waves

The Vrancea region of the southeastern Carpathians is one of the most active seismic zones in Europe and it is well-known for its strong intermediate depth earthquakes. Seismic tomography had revealed a high-velocity body beneath Vrancea and the Moesian platform that extends to a depth of at least 350 km and can be interpreted as descending lithosphere. The strong earthquakes occur within the northeastern part of this high-velocity body, in a very limited seismogenic volume at intermediate depth (70–180 km). Several geodynamic models have been proposed for this area. They can be split into two main categories, in terms of the nature of the high-velocity anomaly, which may (a) be associated with descending relic oceanic lithosphere beneath the bending zone of the SE-Carpathians, either attached or already detached from the continental crust; or (b) it may represent continental lithosphere that has been delaminated, after continental collision and orogenic thickening. Based on currently available information, it appears difficult to distinguish between these two types of models. In this paper we attempt to shed more light on the nature of the seismic anomaly, as well as that of the origin of the intermediate depth seismicity in the Vrancea zone, by investigating the waveform character of P-waves excited by local earthquakes beneath this area, and in particular the dependence of group arrival times on frequency. We present observations of such a dispersion from stations situated at the bending zone of the SE-Carpathians. On the other hand, signals from the same earthquakes, but observed at reference stations outside of the anomalous zone do not show that frequency dependence. A natural explanation for these observations is that it is caused by the presence of a low-velocity channel at the top of the seismic anomaly, which is too thin to be resolved by classical seismic tomographic techniques. Similar observations of dispersed first-arriving P-waves have been made above subduction zones around the world, in which low-velocity layers with a thickness of several kilometers are known to exist. This suggests that a tabular slab of subducted oceanic crust is present within the seismic anomaly under the Vrancea region, and that the anomaly consists of subducted oceanic lithosphere rather than continental lithosphere, at least at depths shallower than the seismically active zone.

Hygrocybe salicis-herbaceae (Agaricomycetes, Hygrophoraceae): an arctic-alpine species new to the South-Eastern Carpathians (Romania)

New localities of <em>Hygrocybe salicis-herbaceae</em> were observed during the research on the fungi of the alpine zone in the Carpathians. This is the first record of this arctic-alpine fungus in the South-Eastern Carpathians. Macro- and micromorphological characters of the Carpathian collections are compared with the descriptions from other regions. A revision of literature data indicates that the sites in the Parâng Mts. reported here are the only known localities of the species from the entire Carpathian range.