The seismic ground motion of a test area in the eastern district of Naples is computed with a hybrid technique based on the mode summation and the finite difference methods. This technique allows us the realistic modelling of source and propagation effects, including local soil conditions. In the modelling, we consider the 1980 Irpinia earthquake, a good example of strong shaking for the area of Naples, which is located about 90 km from the epicenter.The detailed geological setting is reconstructed from a large number of drillings. The sub-soil is mainly formed by alluvial (ash, stratified sand and peat) and pyroclastic materials overlying a pyroclastic rock (yellow neapolitan tuff), representing the neapolitan bedrock. The detailed information available on mechanical properties of the sub-soil and its geometry warrants the application of the sophisticated hybrid technique.As expected, the sedimentary cover causes an increase of the signal's amplitudes and duration. If thin peat layers are present, the amplification effects are reduced, and the peak ground accelerations are similar to those observed for the bedrock model. This can be explained by the backscattering of wave energy at such layers, that tend to seismically decouple the upper from the lower part of the structure.For SH-waves, the influence of the variations of the S-wave velocities on the spectral amplification is studied, by considering locally measured velocities and values determined from near-by down-hole measurements. The comparison between the computed spectral amplifications confirms the key role of an accurate determination of the seismic velocities of the different layers.The comparison performed between a realistic 2-D seismic response and a standard 1-D response, based on the vertical propagation of waves in a plane layered structure, shows considerable difference, from which it is evident that serious caution must be taken in the modelling of expected ground motion at a specific site. 相似文献
A new pterosaur Moganopterus zhuiana gen. et sp. nov. is erected based on a complete skull with lower jaws and anterior cervical vertebrae. It is characterized by much elongated upper and lower jaws with at least 62 total, long, curved teeth with sharp tips, a well developed parietal crest extending posterodorsally, forming an angle of 15 degrees with the ventral margin of the skull, the ratio of length to width of cervical vertebrae greater than 5:1. The skull length is 750 mm, and it is the largest toothed pterosaur found so far in the world. Based on this new pterosaur, the Boreopteridae can be divided into two subgroups: Boreopterinae sub-fam. nov. and Moganopterinae sub-fam. nov., which is also confirmed by the phylogenetic analysis. 相似文献
The U–Pb age determinations of zircon and rutile from the Aar massif reveal a complex evolution of the Central Alpine basement. The oldest components are found in zircons of metasediments, which bear cores of Archean age; the U–Pb age of discordant prismatic zircons of the same rocks ranges between 580 and 680 Ma, an age that is typical for Pan-African metamorphism. The zircons are interpreted as Pan-African detritus with Archean inheritance. The provenance region of the Pan-African zircons is assumed to be a terrane of Gondwana-affinity, i.e. the W. African craton or the Pentevrian microplate. The Caledonian metamorphism left a pervasive structural imprint in amphibolite facies on the rocks of the Aar massif; it is dated at 456±2 and 445 Ma by zircons of a layered migmatitic gneiss and a migmatitic leucosome, respectively, both occurring in the northernmost zones of the massif. Hercynian metamorphism never exceeded greenschist-facies conditions and is recorded by zircon in a garnet-amphibolite and by rutile in a meta-psammite that yield an age of 330 Ma. Both zircon and rutile are considered to be products of retrograde mineral reactions and therefore do not date the peak conditions of Hercynian metamorphism. The Gastern granite at the western end of the Aar massif is a contaminated granite that intruded at 303±4 Ma, contemporaneously with the wide-spread late Hercynian post-collisional I-type magmatism. The study demonstrates the potential of isotope dilution U–Pb dating of single grains and microfractions in deciphering complex evolutionary histories of polymetamorphic terrains. 相似文献
Apatite fission-track and (U-Th)/He analyses require the liberation of intact idiomorphic apatite grains from rock samples. While routinely being carried out by mechanical methods, electrodynamic disaggregation (ED) offers an alternative approach. The high-voltage discharges produced during the ED process create localised temperature peaks (10000 K) along a narrow plasma channel. In apatite, such high temperatures could potentially reduce the length of fission tracks, which start to anneal at temperatures > 60 °C, and could also enhance He diffusion, which becomes significant at 30–40 °C over geological time scales. A comparison of fission-track analyses and (U-Th)/He ages of apatites prepared both by mechanical (jaw crusher, disk mill) and ED processing provides a way of determining whether heating during the latter method has any significant effect. Apatites from three samples of different geological settings (an orthogneiss from Madagascar, the Fish Canyon Tuff, and a muscovite-gneiss from Greece) yielded statistically identical track length distributions compared to samples prepared mechanically. Additionally, (U-Th)/He ages of apatites from a leucogranite from Morocco prepared by both methods were indistinguishable. These first results indicated that during electrodynamic disaggregation apatite crystals were not heated enough to partially anneal the fission tracks or induce significant diffusive loss of He. 相似文献
Cyanuric acid is a suspected gastrointestinal or liver toxicant in humans. Therefore, determination of trace cyanuric acid is very important, in this work a novel, sensitive, and reliable method was developed using differential pulse polarography. Optimum conditions for analytical determination were found to be at a pH of 9.5, Britton–Robinson at a reduction potential of ?105 mV. Experimental results indicate an excellent linear correlation between the peak current and the concentration in the range of cyanuric acid from 0.5 to 27.0 µM (0.06–3.5 µg mL?1) with a correlation coefficient of 0.997. The limit of detection and limit of quantification were obtained as 0.15 and 0.5 µM (0.02–0.06 µg mL?1), respectively. The proposed method was successfully applied to the determination of cyanuric acid in pool water and in spiked milk. Cyanuric acid level in swimming pool water was found as 2.54 ± 0.47 µg mL?1 (19.7 ± 2.29 µM) in swimming pool water for N = 4 and 95% confidence interval. The recoveries were found to be sufficient. Also, the standard deviation of the data was low which shows high accuracy and precision of proposed differential pulse polarographic method. The influences of some other commonly found inorganic salts on the determination of cyanuric acid were also examined. Some interfering species were eliminated using complexing agents, e.g., EDTA. 相似文献