Deep structure of the Racha earthquake source zone from seismic tomography data

The Racha earthquake of 1991 was the strongest of the earthquakes recorded in the Caucasus. It was studied by an international epicentral expedition. Unique data gathered by this expedition included records of aftershocks whose swarm was very intense. A 3-D velocity model is obtained from analysis of these data by the method of local earthquake tomography. The ancient crystalline basement and the sedimentary-volcanic Mesozoic-Cenozoic cover could be identified from cross sections of the P wave field. The eastern and western boundaries of an uplift in the basement of the Dzirulskii Massif are delineated. Linear low velocity heterogeneities correlating with the active Kakheti-Lechkhumi fault zone and two Trans-Caucasian linear fault zones are discovered in the basement. The cloud of aftershock hypocenters is shown to correlate with a reflector coinciding with the cover-basement interface.     

Mathematical modeling of nighttime enhanced electron density regions in the Earth’s ionospheric <Emphasis Type="Italic">F</Emphasis>2 layer and plasmasphere

A mathematical modeling method and the global numerical model of the Earth’s upper atmosphere were used to study nighttime enhanced electron density regions (EEDRs) in the ionospheric F2 layer and their possible manifestations at altitudes of the Earth’s plasmasphere. It has been established that EEDRs are formed owing to latitudinally nonuniform longitudinal (along the magnetic field) plasma flows from the plasmasphere into the nighttime ionosphere and the wind transport of ions along geomagnetic field lines. The specific features of the effect of ionospheric-plasmaspheric plasma transport processes, related to their three-dimensional character, on EEDRs have been revealed.     

Development of Seismic Risk Scenarios Based on a Hybrid Method of Vulnerability Assessment

A hybrid methodology of vulnerability analysis is presented, involving elements from both empirical and theoretical methods. A model for correlating analytically calculated structural damage indices to loss (in monetary terms) is also proposed and calibrated against available statistical data. Probability damage matrices derived using this methodology are incorporated into a cost-benefit model tailored to the problem of estimating the feasibility of seismically rehabilitating the existing stock of reinforced concrete buildings in Thessaloniki, Greece. Losses calculated using the suggested procedure are found to be in good agreement with losses incurred during the 1978 Thessaloniki earthquake. The results of the present study also indicate that benefit/cost ratios for reinforced concrete buildings are quite low. Hence, it appears that a pre-earthquake strengthening programme is not economically justifiable.     

Quantification of the environmental structural risk with spoiling ties: is randomization worthwhile?

Many recent works show that copulas turn out to be useful in a variety of different applications, especially in environmental sciences. Here the variables of interest are usually continuous, being times, lengths, weights, and so on. Unfortunately, the corresponding observations may suffer from (instrumental) adjustments and truncations, and eventually may show several repeated values (i.e., ties). In turn, on the one hand, a tricky issue of identifiability of the model arises, and, on the other hand, the assessment of the risk may be adversely affected. A possible remedy is to adopt suitable randomization procedures: here three different strategies are outlined. The goal of the work is to carry out a simulation study in order to evaluate the effects of the randomization of multivariate observations when ties are present. In particular, it is investigated whether, how, and to what extent, the randomization may change the estimation of the structural risk: for this purpose, a coastal engineering example will be used, as archetypical of a broad class of models and problems in engineering applications. Practical advices and warnings about the use of randomization techniques are hence given.     

Removal of heavy metal ions from drinking water by alginate-immobilised <Emphasis Type="Italic">Chlorella sorokiniana</Emphasis>

This paper investigates the potential of alginate-immobilised Chlorella sorokiniana for removing Cu²⁺, Ni²⁺ and Cd²⁺ ions from drinking water solutions. The effects of initial metal concentrations, contact times and temperatures on the biosorptions and removal efficiencies of the tested metals were investigated at initial pH values of 5, and pH effects were studied within the range of 3–7. When studying the effects of initial metal concentrations, the highest experimental removal yields achieved for Cu²⁺, Ni²⁺ and Cd²⁺ ions were 97.10, 50.94 and 64.61 %, respectively. The maximum biosorption capacities obtained by the Langmuir isotherm model for the biosorptions of Cu²⁺, Ni²⁺ and Cd²⁺ ions by alginate-immobilised C. sorokiniana were found to be 179.90, 86.49 and 164.50 mg/g biosorbent, respectively. The experimental data followed pseudo-second-order kinetics. At an initial metal concentration of 25 mg/L, immobilised algae could be used in at least 5 successive biosorption–desorption cycles. SEM and EDS analyses revealed that the metals bonded to the biosorbent. Bi- and multi-metal systems of Cu²⁺, Ni²⁺ and Cd²⁺ were investigated at initial metal concentrations of 30, 50 and 100 mg/L. The removal of Cd²⁺ as well as Ni²⁺ in such systems was negatively affected by the presence of Cu²⁺. The removal efficiency for Cu²⁺ in multi-metal systems decreased by 5–7 %, whilst in the cases of Cd²⁺ and Ni²⁺ the efficiencies decreased by up to 30 %. Nevertheless, the results obtained show that alginate-immobilised C. sorokiniana can efficiently remove the metals tested from polluted drinking water sources.     

贵州荔波地区2000年来石笋高分辨率的气候记录

通过对荔波董哥洞石笋进行高精度的ICP MS或TIMS U系测年和碳、氧同位素分析,建立了荔波地区2 300a B.P.来高分辨率的古气候变化的时间序列。研究结果表明,贵州荔波地区2 300a B.P.以来石笋记录的季风气候变化,大致可分为8个气候(亚)期:① 2 300～1 800a B.P.为降温期,显示东亚夏季风减弱,东亚冬季风增强,气候干旱寒冷;② 1 800～1 080a B.P.气温有所回升,显示东亚冬季风缓慢减弱,东亚夏季风有所回升,表现为半湿润的温凉气候期;③ 1 080～680a B.P. 为降温期,气温再次下降,显示东亚冬季风再次增强,但降水相对增大,表现为寒冷湿润的气候期,是气候变化的关键转折时期;④ 680～550a B.P.温暖期,显示东亚夏季风再次增强,气温升高,降水增大,表现为温暖湿润的气候期。⑤ 550～400a B.P.寒冷期,显示东亚冬季风快速增强,气温下降,表现为寒冷湿润的气候环境,是近1 000年以来最冷的时期;⑥ 400～364a B.P.温凉期,显示东亚夏季风有所增强,气温有所回升,表现为温凉湿润气候环境;⑦ 364～324a B.P.冷凉期,显示东亚夏季风有所减弱,气温有所下降,表现为冷凉湿润气候环境;⑧ 324a B.P.至今,气候相对波动期,同位素记录曲线呈锯齿状波动,在其内包括若干个冷凉半湿润、冷湿的气候变化亚阶段。根据荔波董哥洞石笋的高分辨率的古气候变化的连续记录,揭示了荔波地区2 300a B.P.以来的一些百年尺度的重大气候事件——干旱寒冷期、隋唐温暖期(或小温暖期)、小寒冷期以及一些十年尺度的降水、温度变化。石笋记录的这种百年、十年尺度的突发性气候变化事件,与冰芯记录极为相似,反映低纬度地区石笋记录的季风气候与高纬度及北极地区的气候具有极好的相关性,这对于认识现代气候系统变化以及对未来十年—百年尺度的气候预测和演化的驱动机制,具有重要的科学意义。     

Marymia: an Archean, amphibolite facies-hosted, orogenic lode-gold deposit overprinted by Palaeoproterozoic orogenesis and base metal mineralisation, Western Australia

The Marymia gold deposit, comprising two orebodies, Keillor 1 and Keillor 2, is at the northern end of the Plutonic Well greenstone belt in the Marymia Inlier, in the southern Capricorn Orogen, just north of the Yilgarn craton. The Marymia Inlier is a discrete fault-bounded Archean gneiss-granitoid-greenstone domain surrounded by sedimentary basins that were formed and variably metamorphosed and deformed during several Palaeoproterozoic orogenic cycles. The greenstone sequence at Marymia is stratigraphically and geochemically similar to greenstone sequences in the Yilgarn craton, but was subjected to further deformation and metamorphism in the Palaeoproterozoic. Late Archean deformation (D1-D2) was ductile to brittle-ductile in style, whereas Palaeoproterozoic deformation was predominantly brittle. Equilibrium mineral assemblages indicate that peak amphibolite-facies metamorphism (540-575 °C, <3 kb) was overprinted by greenschist-facies metamorphism (300-360 °C). Petrographic textures indicate that prograde metamorphism was coeval with D1-D2, with peak metamorphism early to syn D2. Gold mineralisation at Marymia is hosted in metamorphosed tholeiitic basalts and banded iron formation. On a gross scale, the distribution of gold is controlled by D2 folds and shear zones. Lithological contacts with strong rheological or chemical contrasts provide local controls. Gold-related alteration comprises subtle millimetre- to centimetre-wide zones of silicification with variable amounts of quartz, hornblende, biotite, K-feldspar, plagioclase, calcite/siderite, scheelite, titanite, epidote, sulfide and telluride minerals. Quartz veins are generally narrow and discontinuous with low total volume of quartz. Gold is sited in the wall rock, at vein salvedges or within stringers of wall rock within veins. There are two distinct opaque-mineral assemblages: pyrite-pyrrhotite-chalcopyrite-galena and hessite-petzite-altaite-Bi-telluride-galena. Ore samples are variably enriched in Ag, Te, Pb, W, Cu, S and Fe reflecting heterogeneity of the ore mineralogy. Structural timing and temperature of formation of alteration and ore minerals support deposition of gold during late peak amphibolite-facies metamorphism from neutral to alkaline (pH=5-6), moderately oxidising (log P_O2,-21-22) and CO₂-bearing (X_CO2 Ƹ.2) fluids. The total sulfur content of the fluid is estimated at 1mDS. Lead isotope compositions support derivation of lead from within the local greenstone sequence. Gold lodes were deformed by faults and shear zones in the Palaeoproterozoic, with only limited remobilisation. Subeconomic, carbonate vein- and breccia-hosted base metal mineralisation is locally hosted within Palaeoproterozoic fault zones, which clearly cut gold lodes. Base-metal-related alteration is characterised by intense carbonatisation, chloritisation, and albitisation of the mafic host rocks. Mineral assemblages are consistent with formation at greenschist facies conditions. Lead isotope compositions support crystallisation at ca. 1.7 Ga from lead that is similar in composition to earlier gold-related galena.     

Polarization of individual pulses of radio pulsars at the low frequencies 40, 60, and 103 MHz

Measurements of the linear polarization of individual pulses at 40, 60, and 103 MHz are presented for ten pulsars. The degree and position angle of a linear polarization were measured with a temporal resolution of 1–7 ms, and the longitudinal distributions of these parameters were constructed for each pulsar at one or more of these frequencies. These are the first such measurements for pulsars B0031-07, B0320 + 39, B0628-28, and B2217 + 47. Apart from B0628-28, all the pulsars are characterized by the simultaneous presence of orthogonal polarization modes in at least one component of the integral profile. The secondary polarization mode increases at frequencies ≤100 MHz for pulsars whose integrated pulses contain pairs of conal components (B0031-07, B0329 + 54, B0834 + 06, B1133 + 16, B2020 + 28). This is manifested both as an expansion of the longitudinal range where the secondary polarization mode is observed and an increase in its contribution to the emission at a given longitude. New data confirming the dependence of the linear polarization of individual pulses on the intensity and mode of the pulsar emission have been obtained.     

Magnetostratigraphy of the Red Beds in the Hengyang Basin

Abstract This paper discusses the Cretaceous-Tertiary magnetic polarity sequence of the the Hengyang Basin on the basis of magnetostratigraphic study. The age of each stratigraphic unit has been determined with the magnetic polarity time scale combined with ³⁹Ar/⁴⁰Ar dating, thus providing evidence for determining the geological ages of different formations. The authors assign the age of the Dongjing Formation of the Hengyang Basin to Early Cretaceous, the Shenhuangshan Formation to Early-Late Cretaceous, the Daijiaping Formation to Late Cretaceous, and the Dongtang and Xialiushi formations to Palaeocene.     

High-resolution sequence stratigraphy of the Lower Triassic ‘Buntsandstein’ in the Netherlands and northwestern Germany

Detailed log correlations of the largely fluvio-lacustrine Lower Triassic Buntsandstein (Late Permian-Early Anisian), carried out on 80 wells in the Dutch onshore and offshore areas, can be linked to northwest-German high-resolution sequence stratigraphy. The correlations show that cyclic sedimentation occurred in large parts of the basin. Seven 1st-order sequences are recognised, namely the Main Claystone, Rogenstein, Volpriehausen, Detfurth, Hardegsen, Solling and Lower Röt Sequences. They are overlain by the lower part of the Upper Röt–Lower Muschelkalk Sequence. Distinct sequence boundaries have been identified at the bases of four sequences: Volpriehausen, Detfurth, Solling and Upper Röt. The higher-order sequences consist of fining-upwards cycles with a thickness of up to tens of metres. The sequences are laterally persistent and have a characteristic expression on gamma-ray and sonic logs. In the Lower Buntsandstein, they display a uniform character throughout most of the area, with only minor differences in thickness or lithology. NNE-oriented lows and swells were formed during deposition of the Volpriehausen, Detfurth and Hardegsen Sequences. Uplift prior to the deposition of the Solling Sequence caused deep erosion on the swells in the basin and minor erosion in the lows. The high-resolution sequences probably represent alternating, relatively wet and dry climatic periods, with a periodicity of about 100 000 years. An analysis of the sequences suggests that their reduced thickness on the swells is mainly the effect of erosion. This is supported by analyses of the accumulation patterns and rates.