Point Cumulative Semivariogram for Identification of Heterogeneities in Regional Seismicity of Turkey

Geological events are neither isotropic nor homogeneous in their occurrences. These two properties present difficulties for spatial modeling of regionalized variables. This paper presents a point cumulative semivariogram (PCSV) technique for quantifying the heterogeneity characteristics of the phenomenon concerned. The basis of the methodology is to obtain experimental PCSVs for each measurement point which led to estimation of radius of influence around each site. In addition, the experimental PCSVs provide basic information about the heterogeneity of the geological variable in the region, and furthermore many useful interpretations can be made concerning the regional variability of the variable. It provides the measure of cumulative similarity of a regional variable around any measurement site. Because PCSV is a means of measuring total similarity, maps at fixed similarity levels are provided in order to document the regional heterogeneity. Identification of heterogeneities depends on the comparison of fixed PCSV values at a multitude of irregularly scattered sites. The PCSV methodology has been applied to the regional seismic data of Turkey.     

Seismic Zoning of Croatia

The territory of Croatia and neighboring regions is divided into 17 seismic source zones, considering available seismological and geological data. On this basis, seismic hazard elements (seismicity rate, maximum magnitude, b-value, probabilities of exceedance and return periods for a predefined set of magnitudes) are computed using the maximum likelihood method appropriate for treating data-sets with variable completeness thresholds. The values of long term expected peak horizontal acceleration obtained by using a combination of the deterministic and the probabilistic procedure are the highest in the Dubrovnik zone, while the Zagreb zone has the highest earthquake hazard in the continental part of the country. This revised version was published online in June 2006 with corrections to the Cover Date.     

Cenozoic erosion and the preglacial uplift of the Svalbard–Barents Sea region

The creation of the huge fans observed in the western Barents Sea margin can only be explained by assuming extremely high glacial erosion rates in the Barents Sea area. Glacial processes capable of producing such high erosion rates have been proposed, but require the largest part of the preglacial Barents Sea to be subaerial. To investigate the validity of these proposals we have attempted to reconstruct the western preglacial Barents Sea. Our approach was to combine erosion maps based on prepublished data into a single mean valued erosion map covering the whole western Barents Sea and consequently use it together with a simple Airy isostatic model to obtain a first rough estimate of the preglacial topography and bathymetry of the western Barents Sea margin. The mean valued erosion map presented herein is in good volumetric agreement with the sediments deposited in the western Barents Sea margin areas, and as a direct consequence of the averaging procedures employed in its construction we can safely assume that it is the most reliable erosion map based on the available information. By comparing the preglacial sequences with the glacial sequences in the fans we have concluded that 1/2 to 2/3 of the total Cenozoic erosion was glacial in origin and therefore a rough reconstruction of the preglacial relief of the western Barents Sea could be obtained. The results show a subaerial preglacial Barents Sea. Thus, during interglacials and interstadials the area may have been partly glaciated and intensively eroded up to 1 mm/y, while during relatively brief periods of peak glaciation with grounded ice extending to the shelf edge, sediments have been evacuated and deposited at the margins at high rates. The interplay between erosion and uplift represents a typical chicken and egg problem; initial uplift is followed by intensive glacial erosion, compensated by isostatic uplift, which in turn leads to the maintenance of an elevated, and glaciated, terrain. The information we have on the initial tectonic uplift suggests that the most likely mechanism to cause an uplift of the dimensions and magnitude of the one observed in the Barents Sea is a thermal mechanism.     

Tableau de répartition stratigraphique des Grands Foraminifères caractéristiques du Crétacé moyen de la région Méditerranéenne

Le Groupe de Travail Européen des Grands Foraminifères présente un tableau de répartition stratigraphique de 42 espèces bien définies du Crétacé moyen de la région méditerranéenne. La répartition stratigraphique proposée pour chaque espèce est fondée soit sur des propres observations soit sur des données de la littérature supprimer et est contrôlée par la présence d'Ammonites ou de Foraminifères planctoniques.A summarizing account is presented of the deliberations of the research group for Large Foraminifers of the IGCP Project “Mid-Cretaceous Events”. Large Foraminifers are of incontestable value for dating carbonate platform sequences owing to the absence of many other diagnostic groups of organísms. A table of stratigraphical distributions for 42 species is presented.     

Determination of source and palaeoclimate from the comparison of grain and clay fractions in sandstones: A case study

The Paleogene Ke?an Formation of southwestern Turkish Thrace (Alpine Ergene basin) which is dominantly a sandy facies, comprises the Çinarlidere (Lower) and ?aplidere (Upper) members. The turbidite sandstones of the Formation are petrologically defined as multicycle, moderately sorted, angular to subrounded, coarse-skewed, submature graywackes with a detrital clayey matrix of over 15%.The quantitative analyses of light, heavy and clay fractions of sandstone samples from the Ke?an Formation showed marked petrographic variations with grouping of these sediments as Lower- and Upper-member mineralogical facies and led to the following conclusions: a southern terrain with a relatively warm and tropical climate on a terrestrial source of a peneplain topography provided detrital material for the Lower-member sediments (the Biga Massif), while the Upper-member sediments were derived from a rapid erosion of an area of high relief with a uniform supply and continuous infilling of the basin of deposition (a western source terrain: the Rhodope Massif).     

Numerical properties of low-frequency expansions for the reflection and transmission coefficients from transition layers

Summary The numerical properties of the low-frequency expansions for the reflection and transmission coefficients of SH-waves from transition layers, derived in [1], are studied. It is shown that the expansions are suitable for computations only when the thickness d of the transition layer is small in comparison with the wavelength of the incident wave (d0.5). For thicker transition layers, certain modifications of the method are suggested.     

A combined geophysical model of the crust for the south of the European part of the USSR

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Presented at the KAPG Symposium Problems of Interpretation and Construction of Physical Models of Litosphere, Liblice (CSSR), March 6–10, 1978.     

Rain rate estimation from a synergetic use of SSM/I, AVHRR and meso-scale numerical model data

Summary In this paper a retrieval technique for estimating rainfall rates is introduced. The novel feature of this technique is the combination of two satellite radiometers — the Special Sensor Microwave/Imager (SSM/I) and the Advanced Very High-Resolution Radiometer (AVHRR) — with mesoscale weather prediction model data. This offers an adjustment of the model atmospheres to reality which is necessary for calculating brightness temperatures that can be compared with microwave satellite measurements.In sensitivity studies it was found that the estimation of precipitation is determined to a high degree by the particle size distribution of rain and snow, especially by the size distribution of solid hydrometeors. These studies also reveal the influence of the knowledge of the correct cloud coverage inside a SSM/I pixel and the importance of using a realistic temperature profile instead of using standard atmospheres.The retrieval technique is based on radiative transfer calculations using the model of Kummerow et al. (1989). The algorithm consists of two parts: First Guess (FG) brightness temperatures for the SSM/I frequencies are generated as a function of the cloud top height and the cloud coverage, derived from AVHRR data and predictions from a meso-scale model. The rainfall rate of different types of clouds containing raindrops, ice particles and coexisting ice and water hydrometeors is then calculated as a function of the cloud top height. As an example, a strong convective rain event over the western part of Europe and over the Alps is taken to evaluate the performance of this technique. Good agreement with radar data from the German Weather Service was achieved. Compared to statistical rainfall algorithms, the current algorithm shows a better performance of detecting rainfall areas.With 12 Figures     

Weak Contrast PP Wave Displacement R/T Coefficients in Weakly Anisotropic Elastic Media

—Approximate PP plane wave displacement coefficients of reflection and transmission for weak contrast interfaces separating weakly but arbitrarily anisotropic elastic media are presented. The PP reflection coefficient for such an interface has been derived recently by Vavry?uk and P?en?ík (1997). The PP transmission coefficient presented in this paper was derived by the same approach. The coefficients are given as a sum of the coefficient for the weak contrast interface separating two nearby isotropic media and a term depending linearly on contrasts of the so-called weak anisotropy (WA) parameters (parameters specifying deviation of properties of the medium from isotropy), across the interface. While the reflection coefficient depends only on 8 of the complete set of the WA parameters describing P-wave phase velocity in weakly anisotropic media, the transmission coefficient depends on their complete set. The PP reflection coefficient depends on "shear-wave splitting parameter" γ. Tests of accuracy of the approximate formulae are presented on several models.     

Baryt-Kristalle aus Tarna Mare (Rumänien)

Zusammenfassung Auf der Basis von 32 vermessenen Kristallen wird die Morphologie der Baryte von Tarna Mare (Rumänien) diskutiert. Die Kristalle sind alle nach derb-Achse gestreckt. In der Systematik nachBraun liegt ihr Habitus zwischen Typ III (Erztyp) und Typ IV (Karbonattyp).

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Barite crystals from Tarna Mare (Rumania)

Summary On the basis of 32 measured crystals the morphology of the barite from Tarna Mare (Rumania) is discussed. All the crystals are elongated parallel to theb-axis. In the systematics ofBraun, their habitus is intermediate between type III (ore type) and type IV (carbonate type).

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