A cross-border regional earthquake early warning system: PRESTo@CE3RN

Since 2002 the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS) in Udine (Italy), the Agencija Republike Slovenije za Okolje (ARSO) in Ljubljana (Slovenia) and the Zentralanstalt für Meteorologie und Geodynamik (ZAMG) in Vienna (Austria), are collecting, analyzing, archiving and exchanging seismic data in real time, initially in the framework of the EU Interreg IIIa Italia-Austria project “Trans-national seismological networks in the South-Eastern Alps”. As outcome of the successful cooperation, in the 2013 OGS, ARSO and ZAMG decided to officially merge their seismic monitoring efforts into the “Central and Eastern European Earthquake Research Network—CE³RN”. This work reports the results of a nine-month real-time test of the earthquake early warning (EEW) algorithm probabilistic and evolutionary early warning system carried out at the CE³RN. The study allowed identifying the actions to be implemented in order to let the CE³RN become in the next future an efficient cross-border EEW system.

     

On the relation between residual currents and the wind field in the German Bight

Summary The long-period part (T>25 h) of currents measured at close spacing in the German Bight in June 1968 is investigated. The north component of the bottom current is shown to be highly correlated with the east component of the wind in this area, the wind-generated changes of the mass-field giving rise to a quasi-geostrophic current near the bottom.This current responds without perceptible delay to the variations of wind fields with periods considerably longer than those of the seiches of the North Sea. The accelerations linked to such long periods are so small as to be negligable and the residual currents can be regarded as quasi-stationary.

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Über die Beziehung zwischen Reststrom und Windfeld in der Deutschen Bucht

Zusammenfassung Es werden engabständige Strommessungen in der Deutschen Bucht aus dem Juni 1968 in ihrem langperiodischen Teil (T>25 h) untersucht. Dabei ergibt sich, daß die Nordkomponente des Bodenstromes (v) stark korreliert mit der Ostkomponente des Windes (U) in diesem Gebiet. Die winderzeugten Veränderungen des Massenfeldes verursachen eine quasi-geostrophische Strömung am Boden.Diese Strömung reagiert ohne erkennbare Verzögerung auf solche Veränderungen des Windfeldes, die erheblich größere Perioden haben als die Eigenschwingungen der Nordsee. Die damit verbundenen Beschleunigungen sind sehr klein und so zu vernachlässigen; daher kann man die Restströmung auch als quasi-stationär ansehen.

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Sur la relation entre les courants résiduels et le champ du vent en baie Allemande

Résumé La partie à longue période (T>25 h) de courants measurés en des points rapprochés en baie Allemande en juin 1968 est étudiée. La composante Nord du courant de fond se révèle largement corrélée avec la composante Est du vent dans cette zone. Les modifications du champ de masse dues au vent donnent naissance à un courant quasi-géostrophique près du fond.Ce courant répond sans délai perceptible aux variations du champ du vent avec des périodes considérablement plus longues que celles des seiches de la mer du Nord. Les accélérations liées à de telles longues périodes sont si petites qu'elles peuvent être négligées et les courants peuvent être considérés comme quasi-stationnaires.

     

Meeresoptische Messungen während schwerer Stürme auf der Forschungsplattform “Nordsee” vom 14. November bis zum 8. Dezember 1980

Ocean Dynamics - Meeresoptische Messungen auf der Forschungsplattform “Nordsee” haben gezeigt, daß dort während schwerer Stürme, hauptsächlich durch den Einfluß...     

Element budgets of pine stands on lignite and pyrite containing mine soils

To analyze the development of pine ecosystems on lignite and pyrite containing mine soils, four pine stands with ages of 3–35 years were investigated in a chronosequence approach. Bulk precipitation, throughfall and soil solution in depths of 20, 40, 70 and 100 cm were studied over a three-year period to determine element fluxes in these forest ecosystems on extreme acidic and saline soils.Element budgets are controlled by the processes induced by pyrite oxidation such as intensive weathering of primary minerals, precipitation and leaching of secondary phases.Despite low water fluxes, element outputs can reach extraordinary high values due to very high concentrations in the soil solution. Although element outputs decrease drastically with stand age, respectively, site age, they exceed those of comparable pine stands on non-mine sites. Nitrogen release from the lignite fraction represents a special characteristic of the examined substrates. Nitrogen losses beneath the rooted zone can be 34 kg N ha⁻¹ yr⁻¹ in 100 cm depth. Element input and output in the examined ecosystems are far from balance. Closed cycling of nutrients seems to be recognizable in the case of potassium.     

Archaean high-K granitoids produced by remelting of earlier Tonalite–Trondhjemite–Granodiorite (TTG) in the Sangmelima region of the Ntem complex of the Congo craton,southern Cameroon

We present a geochemical and isotopic study that, consistent with observed field relations, suggest Sangmelima late Archaean high-K granite was derived by partial melting of older Archaean TTG. The TTG formations are sodic-trondhjemitic, showing calcic and calc-alkalic trends and are metaluminous to peraluminous. High-K granites in contrast show a potassic calc-alkaline affinity that spans the calcic, calc-alkalic, alkali-calcic and alkalic compositions. The two rock groups (TTG and high-K granites) on the other hand are both ferroan and magnesian. They have a similar degree of fractionation for LREE but a different one for HREE. Nd model ages and Sr/Y ratios define Mesoarchaean and slab-mantle derived magma compositions respectively, with Nb and Ti anomalies indicating a subduction setting for the TTG. Major and trace element in addition to Sr and Nd isotopic compositions support field observations that indicate the derivation of the high-K granitic group from the partial melting of the older TTG equivalent at depth. Geochemical characteristics of the high-K granitic group are therefore inherited features from the TTG protolith and cannot be used for determining their tectonic setting. The heat budget required for TTG partial melting is ascribed to the upwelling of the mantle marked by a doleritic event of identical age as the generated high-K granite melts. The cause of this upwelling is related to linear delamination along mega-shear zones in an intracontinental setting.     

Unusual exsolution phenomena in omphacite and partial replacement of phengite by phlogopite + kyanite in an eclogite from the Erzgebirge

In the Erzgebirge Crystalline Complex, eclogites occur in three different high pressure (HP) units (1, 2 and 3) recording contrasting pressure (P)–temperature (T) conditions. Eclogites from HP-unit 1 experienced peak metamorphic conditions in the coesite stability field at about 33 kbar/850 °C. Commonly, these eclogites from HP-unit 1 are all very similar, with an eclogitic peak assemblage of omphacite–garnet–coesite–K-feldspar, rarely accompanied by kyanite, and omphacites systematically deviating from a stoichiometric composition. In contrast, an eclogite recently found near Blumenau, is mineralogically and geochemically different from the typical eclogites of HP-unit 1. This unusual eclogite reveals the eclogitic equilibrium assemblage omphacite–garnet–coesite–phengite–phlogopite–kyanite, and yields metamorphic peak conditions of 870 °C and >29 kbar. There is clear textural evidence of the formation of phlogopite and kyanite under partial consumption of phengite and garnet. Moreover, the omphacite is stoichiometric and contains abundant exsolution lamellae, the thickest of which were identified as quartz by the electron microprobe. The finer lamellae were studied by transmission electron microscopy (TEM). Oligoclase was identified as an exsolution phase. Other lamellae proved to consist of K-white mica, also interpreted as exsolution. Prior to exsolution, the omphacite composition must have been cation-deficient, as that of the other, common HP-unit 1 eclogites. These non-stoichiometric compositions are ascribed to partial substitution by the Ca-Eskola pyroxene component, which calculates to an average of 8 mol% for omphacite in HP-unit 1 eclogites. According to experiments, this substitution becomes significant at P > 30 kbar. Exsolution of K-white mica may indicate hydroxyl defects in the original omphacite, also favoured by high pressure. Oligoclase and K-white mica exsolution from Ca-Eskola-rich clinopyroxene has not previously been reported. The omphacite has a disordered C2/c structure; and in just one case very small (a few tens of nanometres) antiphase domains, resulting from the C2/c to P2/n transformation, are present. These features may indicate a brief thermal history and rapid tectonic processes. Received: 4 January 1999 / Accepted: 20 April 2000     

Transmission electron microscopic study of antiphase domains in CaAl2Ge2O8-Feldspar

Transmission electron microscopic study of synthetic CaAl₂Ge₂O₈-feldspar revealed two types of antiphase domains: type “b”-antiphase domains with the displacement vector 1/2 [110] and type “c”-antiphase domains with the displacement vector 1/2 [111]. The “b”-domains were on the order of 0.1 μm in size, while the “c”-domains displayed wall to wall distances mostly between 0.1 and 1 μm. The formation of the two types of antiphase domains is due to reductions in translational symmetry associated with the phase transitions \(C\bar 1 \to I\bar 1 \to P\bar 1\) . The antiphase domain textures of CaAl₂Ge₂O₈-feldspar are very similar to the textures found in natural and synthetic anorthite, CaAl₂Si₂O₈.     

Fe-Ni-Co-O-S Phase Relations in Peridotite-Seawater Interactions

Serpentinization of abyssal peridotites is known to produceextremely reducing conditions as a result of dihydrogen (H₂,aq)release upon oxidation of ferrous iron in primary phases toferric iron in secondary minerals by H₂O. We have compiled andevaluated thermodynamic data for Fe–Ni–Co–O–Sphases and computed phase relations in fO₂,g–fS₂,g andaH₂,aq–aH₂S,aq diagrams for temperatures between 150 and400°C at 50 MPa. We use the relations and compositions ofFe–Ni–Co–O–S phases to trace changesin oxygen and sulfur fugacities during progressive serpentinizationand steatitization of peridotites from the Mid-Atlantic Ridgein the 15°20'N Fracture Zone area (Ocean Drilling ProgramLeg 209). Petrographic observations suggest a systematic changefrom awaruite–magnetite–pentlandite and heazlewoodite–magnetite–pentlanditeassemblages forming in the early stages of serpentinizationto millerite–pyrite–polydymite-dominated assemblagesin steatized rocks. Awaruite is observed in all brucite-bearingpartly serpentinized rocks. Apparently, buffering of silicaactivities to low values by the presence of brucite facilitatesthe formation of large amounts of hydrogen, which leads to theformation of awaruite. Associated with the prominent desulfurizationof pentlandite, sulfide is removed from the rock during theinitial stage of serpentinization. In contrast, steatitizationindicates increased silica activities and that high-sulfur-fugacitysulfides, such as polydymite and pyrite–vaesite solidsolution, form as the reducing capacity of the peridotite isexhausted and H₂ activities drop. Under these conditions, sulfideswill not desulfurize but precipitate and the sulfur contentof the rock increases. The co-evolution of fO₂,g–fS₂,gin the system follows an isopotential of H₂S,aq, indicatingthat H₂S in vent fluids is buffered. In contrast, H₂ in ventfluids is not buffered by Fe–Ni–Co–O–Sphases, which merely monitor the evolution of H₂ activitiesin the fluids in the course of progressive rock alteration.The co-occurrence of pentlandite–awaruite–magnetiteindicates H₂,aq activities in the interacting fluids near thestability limit of water. The presence of a hydrogen gas phasewould add to the catalyzing capacity of awaruite and would facilitatethe abiotic formation of organic compounds. KEY WORDS: serpentinization; ODP Expedition 209; sulfide; oxygen fugacity; sulfur fugacity; hydrothermal system; metasomatism; Mid-Atlantic Ridge     

Zircon Hf isotope perspective on the origin of granitic rocks from eastern Bavaria, SW Bohemian Massif

The petrogenetic potential of in situ laser ablation Hf isotope data from melt precipitated zircons was explored through the analyses of about 700 individual crystals derived from about 20 different granitic intrusions covering the Variscan basement segment of eastern Bavaria, SE Germany. In combination with geochemical features, four major suites of granitic rocks can be distinguished: (1) NE Bavarian redwitzites (52–57 wt% SiO₂, intrusion ages around 323 Ma) have chondritic εHf(t) values (+0.8 to –0.4). The redwitzites are hybrid rocks and the Hf data are permissive of mixing of a mantle progenitor and crustal melts. (2) Various intermediate rock types (dioritic dyke, granodiorite, palite, 59–63 wt% SiO₂, 334–320 Ma) from the Bavarian Forest yield negative εHf(t) values between –3.4 and –5.1. These values which apparently contradict a mantle contribution fingerprint an enriched (metasomatized) mantle component that was mixed with crustal material. (3) Voluminous, major crust forming granites sensu stricto (67–75 wt% SiO₂, 328–298 Ma) are characterized by a range in εHf(t) values from –0.5 to –5.6. Different crustal sources and/or modification of crustal melts by various input of juvenile material can explain this variation. (4) Post-plutonic (c. 299 Ma) porphyritic dykes of dacitic composition (64–67 wt% SiO₂) from the southern Bavarian Forest have chondritic εHf(t) values (+0.6 to –1.1) and display large intergrain Hf isotope variation. The dykes form a separate petrogenetic group and the Hf data suggest that the zircons crystallized when a pristine mantle-derived parental melt was modified by infiltration of crustal material. The zircon Hf data form a largely coherent positive array with the whole-rock Nd data and both systems yield similar two-stage depleted mantle model ages (1.1–1.7 Ga).