Deep electrical structure under central Europe

Summary The model of the electrical conductivity distribution within the Bohemian Massif to mid-upper mantle depths was derived from magnetotelluric and magnetic continuum long-period data of the Budkov Observatory (Geophysical Institute, Acad. Sci. Czech Republic., Prague) and from the ISL (Induction Scale Lengths) data of the Prhonice Observatory. The ranges of apparent resistivities in the Bohemian Massif (BM) are compared with those obtained at relevant central European observatories. The conductivity profile is estimated from the resistivity/depth graph corresponding to substitute perfect conductor inversion.Dedicated to the Memory of Professor Karel P     

The generation of MHD shock waves during the impulsive phase of the February 27, 1992 flare

In this paper a unique 2.3–4.2 GHz radio spectrum of the flare impulsive phase, showing fast positively drifting bursts superimposed on a slowly negatively drifting burst, is presented. Analyzing this radio spectrum it was found that the flare started somewhere near the transition region, where upward propagating MHD waves were generated during the whole impulsive phase. Moreover, it was found that behind a front of these ascending MHD waves the downward propagating electron beams, which bombarded dense layers of the solar atmosphere, were accelerated. It seems that, simultaneously with the increase of beam bombardment intensity, the intensity of MHD waves was increasing and thus the MHD shock wave generation and the electron beam acceleration and bombardment formed a self-consistently amplifying flare process. At higher coronal heights this process was followed by a type II radio burst, i.e. by the MHD flare shock. To verify this concept, the numerical modeling of the shock-wave generation and propagation in space from a flare site near the transition region up to 3 solar radii was made. Comparing the thermal and magnetic field disturbances, it was found that those of magnetic origin are more relevant in this case. Combining the results of interpretation and numerical simulation, a model of the February 27, 1992 flare is suggested and new aspects of this model are discussed.     

A test of GEM T2 from GEOSAT crossovers using latitude lumped coefficients

Summary New Latitude Lumped Coefficients (LLC) of a geopotential model are defined as representing the principal differences of the radial distance to a satellite due to the model at single-orbit crossovers in an Exact Repeat Mission. In contrast with previously defined orbital lumped coefficients, the LLC here are dependent only on the geopotential order (without degree distinction) and the latitude. We examine discrepancies in altimetrically determined sea surface heights at over 30000 crossover positions of GEOSAT during its ERM, 1986–1989, after removal of many variable media and surface effects (Cheney et al., 1991) as well as initial condition orbit error. The mean of these discrepancies along well represented latitude bands in the southern hemisphere are used to determine the LLC errors for Goddard Earth Model T2, which was the reference for the GEOSAT sea surface heights. GEM T2 was derived from satelliteonly tracking data with good representation of the GEOSAT orbit. Relating the measured LLC discrepancies to projections of commission error from the GEM T2 variance-covariance matrix, we find that — except for order 3 — GEM T2's performance is as expected. This test represents the first spectral calibration of a gravity model with independent, purely radial orbit data.     

Landslide databases in the Geological Surveys of Europe

Landslides are one of the most widespread geohazards in Europe, producing significant social and economic impacts. Rapid population growth in urban areas throughout many countries in Europe and extreme climatic scenarios can considerably increase landslide risk in the near future. Variability exists between European countries in both the statutory treatment of landslide risk and the use of official assessment guidelines. This suggests that a European Landslides Directive that provides a common legal framework for dealing with landslides is necessary. With this long-term goal in mind, this work analyzes the landslide databases from the Geological Surveys of Europe focusing on their interoperability and completeness. The same landslide classification could be used for the 849,543 landslide records from the Geological Surveys, from which 36% are slides, 10% are falls, 20% are flows, 11% are complex slides, and 24% either remain unclassified or correspond to another typology. Most of them are mapped with the same symbol at a scale of 1:25,000 or greater, providing the necessary information to elaborate European-scale susceptibility maps for each landslide type. A landslide density map was produced for the available records from the Geological Surveys (LANDEN map) showing, for the first time, 210,544 km² landslide-prone areas and 23,681 administrative areas where the Geological Surveys from Europe have recorded landslides. The comparison of this map with the European landslide susceptibility map (ELSUS 1000 v1) is successful for most of the territory (69.7%) showing certain variability between countries. This comparison also permitted the identification of 0.98 Mkm² (28.9%) of landslide-susceptible areas without records from the Geological Surveys, which have been used to evaluate the landslide database completeness. The estimated completeness of the landslide databases (LDBs) from the Geological Surveys is 17%, varying between 1 and 55%. This variability is due to the different landslide strategies adopted by each country. In some of them, landslide mapping is systematic; others only record damaging landslides, whereas in others, landslide maps are only available for certain regions or local areas. Moreover, in most of the countries, LDBs from the Geological Surveys co-exist with others owned by a variety of public institutions producing LDBs at variable scales and formats. Hence, a greater coordination effort should be made by all the institutions working in landslide mapping to increase data integration and harmonization.     

Integrated foraminifera and δ<Superscript>13</Superscript>C stratigraphy across the Cenomanian–Turonian event interval in the eastern Baltic (Lithuania)

The Cenomanian–Turonian transition marks one of the most important extinction episodes of the Mesozoic era. This extinction event was associated with the development of widespread oceanic anoxia and pronounced stable carbon isotopic excursion. Despite its importance, the effects of the perturbation on higher latitude biotas, and from the Baltic region in particular, are currently underexplored. Therefore, in this contribution we present the fossil record of a foraminifera succession integrated with δ¹³C trends from two deep cores: Bliūdsukiai-19 from western Lithuania and Balta?i?k?-267 from southern Lithuania. Two foraminiferal zones were distinguished: Rotalipora cushmani from the upper Cenomanian and Whiteinella archaeocretacea from the boundary strata between the Cenomanian and Turonian in the Balta?i?k?-267 core section, and a W. archaeocretacea Zone in the Bliūdsukiai-19 core section. A chemostratigraphical analysis of the stable carbon isotopes revealed a positive Cenomanian–Turonian δ¹³C anomaly, with maximum values reaching 3.57‰ in the upper part of the Bliūdsukiai-19 core section. A non-metric multidimensional scaling analysis of the foraminifera communities revealed that the major changes in their assemblages were strongly temporally organized and associated with the changes in the stable carbon isotopic ratios. This fact points to the significant effects of the C–T extinction event on the northern Neotethys paleocommunities.     

A 1D Hypoplastic constitutive model for expansive soils

This paper presents a simple hypoplastic constitutive model that describes the essential features of the material behaviour of partially saturated clayey soils observed in oedometric compression tests. The model is formulated in terms of net stress and degree of saturation. The total strain rate is decomposed into a portion related to the changes in saturation and a portion for the evolution of net stress. However, no distinction is made between plastic and elastic strains. With this strain rate decomposition, the maximum swelling strain/stress are obtained by simulating wetting processes under constant stress/strain conditions. In addition to the void ratio, the model includes two scalar variables to track the loading history (preloading). The calibration of the model constants using common laboratory tests is discussed. Confined and unconfined swelling tests under oedometric conditions with subsequent loading and unloading phases carried out on three different materials were satisfactorily simulated by the model. Its promising results call for an extension to a 3D formulation.

     

Automated calibration of advanced soil constitutive models. Part II: hypoplastic clay and modified Cam-Clay

This paper introduces an automated deterministic method for the calibration of the Modified Cam-Clay and hypoplastic clay model. The calibration is structured in a hierarchical order established based on the apriori sensitivity study performed. The proposed method favours the clear physical meaning of the model parameters to a complete optimization of the objective error function. The method requires only basic laboratory experiments and it is currently implemented in the free-to-use online application called ExCalibre.

     

On the automatic parameter calibration of a hypoplastic soil model

Acta Geotechnica - This paper presents an approach for the automatic parameter calibration (AC) of a hypoplastic constitutive soil model. The calibration software developed in this work simplifies...     

Mineralogy of Copper in Sulfide-Free Endogenic Pb–Zn–Sb Mineralization of the Pelagonian Massif,Republic of North Macedonia

Geology of Ore Deposits - Behavior of copper in sulfide-free metasomatic ores of the Pelagonian massif, Republic of North Macedonia has been studied. It is shown that the highest copper activity...