Pinios (Peneus) River (Central Greece): Hydrological — Geomorphological elements and changes during the quaternary

The Pinios River is the third longest river of Greece. It drains the entire drainage basin of Thessaly (eastern part of Central Greece), part of which is the largest plain of the country. In this research the hydrological, geomorphological and geological characteristics of the riverine area of Pinios were studied. Classification and grouping of these characteristics were then carried out, which led to the segmentation of the Pinios River into seven sections, each one with its own set of thematic data. These sets assign separate functions and evolutions of the river system during the Quaternary. Specifically, the basin of the present Pinios River, before its evolution into a river basin, comprised three separate and independent systems. The present Pinios River emerged as a river system from the merging of the lacustrine paleoenvironments along with the major tributaries that drained large parts of the present hydrological basin and as soon as the karstic openings of the central hill valley and the Tempi valley took place during the Quaternary. The followed methodology for the segmentation of the river can be used for the study of heterogeneous river systems.     

Phosphorus zoning as a recorder of crystal growth kinetics: application to second-generation olivine in mantle xenoliths from the Cima Volcanic Field

Composite mantle xenoliths from the Cima Volcanic Field (CA, USA) contain glassy veins that cross-cut lithologic layering and preserve evidence of lithospheric melt infiltration events. Compositions and textures of minerals and glasses from these veins have the potential to place constraints on the rates and extents of reaction during infiltration. We studied glass-bearing regions of two previously undescribed composite xenoliths, including optical petrography and chemical analysis for major and trace elements by electron probe microanalysis and laser-ablation inductively coupled plasma mass spectrometry. The petrogenetic history of each vein involves melt intrusion, cooling accompanied by both wall-rock reaction and crystallization, quench of melt to a glass, and possibly later modifications. Exotic secondary olivine crystals in the veins display concentric phosphorus (P)-rich zoning, P-rich glass inclusions, and zoning of rapidly diffusing elements (e.g., Li) that we interpret as records of rapid disequilibrium events and cooling rates on the order of 10 °C/h. Nevertheless, thermodynamic modeling of the diversity of glass compositions recorded in one of the samples demonstrates extensive reaction with Mg-rich olivine from the matrix before final quench. Our results serve as a case study of methods for interpreting the rates and processes of lithospheric melt-rock reactions in many continental and oceanic environments.     

An estimate of probabilistic seismic hazard for five cities in Greece by using the parametric-historic procedure

A probabilistic procedure was applied to assess seismic hazard for the sites of five Greek cities (Athens, Heraklion, Patras, Thessaloniki and Volos) using peak ground acceleration as the hazard parameter. The methodology allows the use of either historical or instrumental data, or a combination of both. It has been developed specifically for the estimation of seismic hazard at a given site and does not require any specification of seismic sources or/and seismic zones. A new relation for the attenuation of peak ground acceleration was employed for the shallow seismicity in Greece. The computations involved the area- and site-specific parts. When assessing magnitude recurrence for the areas surrounding the five cities, the maximum magnitude, m_max, was estimated using a recently derived equation. The site-specific results were expressed as probabilities that a given peak ground acceleration value will be exceeded at least once during a time interval of 1, 50 and 100 years at the sites of the cities. They were based on the maximum peak ground acceleration values computed by assuming the occurrence of the strongest possible earthquake (of magnitude m_max) at a very short distance from the site and using the mean value obtained with the help of the attenuation law. This gave 0.24 g for Athens, 0.53 g for Heraklion (shallow) and 0.39 g Heraklion (intermediate-depth seismicity), 0.30 g for Patras, 0.35 g for Thessaloniki and 0.30 g for Volos. In addition, the probabilities of exceedance of the estimated maximum peak ground acceleration values were calculated for the sites. The standard deviation of the new Greek attenuation law demonstrates the uncertainty and large variation of predicted peak ground acceleration values.     

b-Values of two tectonic parts in the circum-pacific belt

Two different data sets have been applied to compute theb-parameter of the magnitude-frequency relation for two different areas in the circum-Pacific belt. These areas are: a) South America, Middle America and Mexico, b) all the remaining island arcs of the circum-Pacific belt, starting from Alaska and the Aleutian islands and proceeding southeastwards. The first data set spreads over 77 years, while the second one covers a 90-year period. In both cases the results clearly showed that theb-values are lower in the first of the above-mentioned areas, while respectively higher in the second. This is due to the tectonic conditions in these areas as estimated during the present work.     

Dimensional response analysis of yielding structures with first‐mode dominated response

This paper introduces a new way of estimating the inelastic response of first‐mode dominated structures with behaviour that can be approximated with the elastoplastic idealization. The proposed approach emerges from formal dimensional analysis and is liberated from the response of the elastic system. The application of the proposed method hinges upon the existence of a distinct time scale and a length scale that characterize the most energetic component of the ground shaking. Such time and length scales emerge naturally from the distinguishable pulses which dominate a wide class of strong earthquake records; they are directly related with the rise time and slip velocity of faulting, and can be formally extracted with validated mathematical models published in the literature. The most decisive feature of this work is that the inelastic response curves that result with the proposed approach assume similar shapes for different values of the normalized yield displacement. Because of this similarity the paper proposes a single inelastic response curve which offers directly the maximum inelastic displacement of the structure given the energetic pulse period and pulse amplitude of the ground shaking. When the proposed method is applied to MDOF structures it is not capable to estimate interstorey drifts nor is capable to capture the effects of negative stiffness which may result due to P‐delta effect. Copyright © 2006 John Wiley & Sons, Ltd.     

Remnants of boninitic melts in the upper mantle beneath the central Pannonian Basin?

Summary We present a detailed textural and compositional study of two orthopyroxene-rich olivine websterites. One occurs as a vein in a harzburgite xenolith and the other is an individual xenolith, both found at Szentbékkálla in the Bakony–Balaton Highland Volcanic Field (central Pannonian Basin, western Hungary). The textural features of these orthopyroxene-rich rocks suggest that they crystallized from silicate melts to form veins in peridotite mantle rock. Their geochemical features, such as the presence of Al₂O₃-poor orthopyroxenes, Cr-rich spinels, and clinopyroxenes with U-shaped chondrite-normalized REE-patterns, indicate that the vein material formed from Mg-rich silicic (boninitic) melts at mantle depths. The olivine fabric investigation of both the veins and the wall-rock suggest that the development of the veins was followed by subsequent recrystallization during the Cenozoic evolution of the Carpathian–Pannonian region.     

Intrusion of shoshonitic magmas at shallow crustal depth: <Emphasis Type="Italic">T</Emphasis>–<Emphasis Type="Italic">P</Emphasis> path,H<Subscript>2</Subscript>O estimates,and AFC modeling of the Middle Triassic Predazzo Intrusive Complex (Southern Alps,Italy)

The multi-pulse shoshonitic Predazzo intrusive complex represents an ideal igneous laboratory for investigating the chemical and physical conditions of magma emplacement in a crustal context, since numerical models can be constrained by field evidence. It constitutes the most intriguing remnant of the Middle Triassic magmatic systems of the Dolomitic Area (Southern Alps), preserved by the Alpine tectonics. Predazzo Intrusive Complex comprises silica saturated (pyroxenites/gabbros to syenites), silica undersaturated (gabbros to syenites), and silica oversaturated (granites and syenogranites) rock suites. In this paper, we modeled its emplacement and evolution with a multiple thermo-/oxy-barometric, hygrometric, and EC-AFC approach. At odds with what proposed in literature but according to the field evidence, the emplacement of the Predazzo Intrusive Complex occurred at shallow depth (<?6 km). In this context, the different pulses differed slightly in bulk water content, but shared a common thermal regime, with temperatures between 1000 and 1100 °C and ~?600 °C at low-to-moderate oxidizing conditions (? 0.1 to +?0.7 ΔFMQ). The interaction between the intrusion and the shallow crustal rocks was minimal, with Sr and Nd isotopic compositions indicating an average of 5–6% assimilation of crust. A thermo- and oxy-barometric comparison with the nearby Mt. Monzoni also enabled to speculate about the solidification time of the intrusion, which we infer took place over about 700 ka.