Marine Stone Columns to Prevent Earthquake Induced Soil Liquefaction

With ports and other near shore structures expanding, and regions previously not considered prone to earthquakes being re-classified after recent earthquake events, ground improvement by stone columns is increasingly considered to improve loose or soft in situ soils. The Dry Bottom Feed Stone Column construction technique can be used under water if a double-lock stone delivery system is attached to the vibroprobe. The use of pneumatic stone transport from the barge into the vibroprobe receiver tank makes it possible to reach large water and treatment depths. Digital recording of all relevant operation parameters provides a very high level of quality assurance, including a diameter-over-depth profile for each stone column. An introduction to earthquake-resistant design of stone columns and guidelines for specifying Marine Stone Columns are given.     

Reconstruction of floral changes during deposition of the Miocene Embalut coal from Kutai Basin,Mahakam Delta,East Kalimantan,Indonesia by use of aromatic hydrocarbon composition and stable carbon isotope ratios of organic matter

The distribution of aromatic hydrocarbons and stable carbon isotope ratios of organic matter in a series of nine Miocene Embalut coal samples obtained from nine coal seams of Kutai Basin, East Kalimantan, Indonesia were studied. The rank of the Embalut coals ranged from lignites to low rank sub-bituminous coals (0.36–0.50% Rr), based on measurements of huminite reflectance. The aromatic hydrocarbon fractions of all coal samples were dominated by cadalene in the lower boiling point range and picene derivatives in the higher boiling point range of the gas chromatograms. Cadalene can be attributed to the contribution of Dipterocarpaceae and various hydrated picenes to the contribution of additional angiosperms to the coal forming vegetation. The picenes originate from alpha- and beta-amyrin. However, in some coal samples minor amounts of simonellite and retene were also detected which argues for an additional contribution of gymnosperms (conifers) to coal forming vegetation preferentially in the Middle Miocene and at the beginning of the Late Miocene. The results of stable carbon isotope ratios (δ¹³C) in most of the coal samples are consistent with their origin from angiosperms (δ¹³C between ?27.0‰ and ?28.0‰). During the Miocene the climate of Mahakam Delta was not uniformly moist and cooler than the present day climate. This would have been favourable for the growth of conifers, especially in the montane forests. The contribution of conifers to the Embalut coals might be a result of the cool Middle/Late Miocene climate during peat accumulation in the Kutai Basin.     

南极菲尔德斯半岛海鸟与种群分布

2000/2001-2002/2003南极夏季期间,对中国南极长城站所在地乔治王岛菲尔德斯半岛及邻近区海鸟群落组成与种群分布特征进行了观测研究。本文报道了对该地区三次考察期间记录的海鸟共11科25种。其中,有繁殖活动的海鸟12种,优势种有白眉企鹅(Pygoscelispapua)和黄蹼洋海燕(Oceanitesoceanicus),常见种有纹颊企鹅(Pygoscelisantarctica)、巨鹱(Macronectesgiganteus)、花斑鹱(Daptioncapenis)、南极燕鸥(Sternavittata)和灰贼鸥(Catharactaantarctica)等。     

Field evidence for the control of grain size and sediment supply on steady‐state bedrock river channel slopes in a tectonically active setting

We exploit a natural experiment in Boulder Creek, a ~ 30 km² drainage in the Santa Cruz mountains, CA, USA to explore how an abrupt increase in the caliber of bedload sediment along a bedrock channel influences channel morphology in an actively uplifting landscape. Boulder Creek's bedrock channel, which is entirely developed on weak sedimentary rock, has a high flow shear stress that is about 3.5 times greater where it transports coarse (~ 22 cm D₅₀) diorite in the lower reaches in comparison with the upstream section of the creek that transports only relatively finer bedload (~2 cm D₅₀) derived from weak sedimentary rocks. In addition, Boulder Creek's channel abruptly widens and shallows downstream and transitions from partial to nearly continuous alluvial cover where it begins transporting coarse diorite. Boulder Creek's tributary channels are also about three times steeper where they transport diorite bedload, and within the Santa Cruz mountains channels in sedimentary bedrock are systematically steeper when >50% of their catchment area is within crystalline basement rocks. Despite this clear control of coarse sediment size on channel slopes, the threshold of motion stress for bedload, alone, does not appear to control channel profile slopes here. Upper Boulder Creek, which is starved of coarse sediment, maintains high flow shear stresses well in excess of the threshold for motion. In contrast, lower Boulder Creek, with a greater coarse sediment supply, exerts high flow stresses much closer to the threshold for motion. We speculate that upper Boulder Creek has evolved to sustain partial alluvial cover and transfer greater energy to the bed via bedload impacts to compensate for its low coarse sediment supply. Thus bedload supply, bedrock erosion efficiency, and grain size all appear to influence channel slopes here. Copyright © 2017 John Wiley & Sons, Ltd.     

How representative are subfossil assemblages of Chironomidae and common benthic invertebrates for the living fauna of Lake De Waay,the Netherlands?

The distribution of benthic invertebrates and their subfossil remains was examined within the basin of De Waay, a dimictic, eutrophic lake in the Netherlands. We focused on Chironomidae, but also report the abundances of 11 invertebrate groups that potentially produce chitinous remains that are preserved in the fossil record, although their remains could only be identified at a coarser taxonomic resolution. Most living invertebrates sampled in different seasons were constrained to the littoral zone, with the exception of a few taxa (Ceratopogonidae, Chaoborus flavicans, and Chironomus) that are adapted to low oxygen conditions in the seasonally anoxic profundal zone. In contrast, assemblages of invertebrate remains in lake surface sediments were similar in the entire lake basin, suggesting that considerable numbers of invertebrate remains are transported and redeposited off-shore in Lake De Waay, due to its steep bathymetry. These results indicate that a single sediment sample obtained from the centre of this lake contains subfossil invertebrate remains originating from the entire lake basin. In Lake De Waay, the majority of taxa found in the living assemblages were identified as remains in lake surface sediments, at least for the Chironomidae that could be identified at a similar taxonomic level in living and subfossil assemblages. Of the total 44 chironomid taxa found in Lake De Waay, 35 taxa occurred in the living assemblages and 34 taxa occurred in the subfossil assemblages. Thirty chironomid taxa occurred both as living and subfossil specimens, and on average these 30 taxa represent 94% of the specimens encountered in a sediment sample. Five rare chironomid taxa present as living larvae were not detected in the subfossil assemblages. Conversely, eight rare and four common chironomid taxa were found in subfossil remains, but not in living assemblages. Our results indicate that subfossil assemblages in surface sediment samples provide spatially integrated and representative samples of the living assemblage. However, a combined approach examining both the living benthic invertebrate fauna and invertebrate remains in lake surface sediments will potentially give a more complete and detailed overview of benthic invertebrates in a lake ecosystem than an approach based exclusively on one of these groups.     

The behavior of trace elements during the chemical evolution of the H2O-, B-, and F-rich granite–pegmatite–hydrothermal system at Ehrenfriedersdorf, Germany: a SXRF study of melt and fluid inclusions

Detailed melt and fluid inclusion studies in quartz hosts from the Variscan Ehrenfriedersdorf complex revealed that ongoing fractional crystallization of the highly evolved H₂O-, B-, and F-rich granite magma produced a pegmatite melt, which started to separate into two immiscible phases at about 720°C, 100 MPa. With cooling and further chemical evolution, the immiscibilty field expanded. Two conjugate melts, a peraluminous one and a peralkaline one, coexisted down to temperatures of about 490°C. Additionally, high-salinity brine exsolved throughout the pegmatitic stage, along with low-density vapor. Towards lower temperatures, a hydrothermal system gradually developed. Boiling processes occurred between 450 and 400°C, increasing the salinities of hydrothermal fluids at this stage. Below, the late hydrothermal stage is dominated by low-salinity fluids. Using a combination of synchrotron radiation-induced X-ray fluorescence analysis and Raman spectroscopy, the concentration of trace elements (Mn, Fe, Zn, As, Sb, Rb, Cs, Sr, Zr, Nb, Ta, Ag, Sn, Ta, W, rare earth elements (REE), and Cu) was determined in 52 melt and 8 fluid inclusions that are representative of distinct stages from 720°C down to 380°C. Homogenization temperatures and water contents of both melt and fluid inclusions are used to estimate trapping temperatures, thus revealing the evolutionary stage during the process. Trace elements are partitioned in different proportions between the two pegmatite melts, high-salinity brines and exsolving vapors. Concentrations are strongly shifted by co ncomitant crystallization and precipitation of ore-forming minerals. For example, pegmatite melts at the initial stage (700°C) have about 1,600 ppm of Sn. Concentrations in both melts decrease towards lower temperatures due to the crystallization of cassiterite between 650 and 550°C. Tin is preferentially fractionated into the peralkaline melt by a factor of 2–3. While the last pegmatite melts are low in Sn (64 ppm at 500°C), early hydrothermal fluids become again enriched with about 800 ppm of Sn at the boiling stage. A sudden drop in late hydrothermal fluids (23 ppm of Sn at 370°C) results from precipitation of another cassiterite generation between 400 and 370°C. Zinc concentrations in peraluminous melts are low (some tens of parts per million) and are not correlated with temperature. In coexisting peralkaline melts and high-T brines, they are higher by a factor of 2–3. Zinc continuously increases in hydrothermal fluids (3,000 ppm at 400°C), where the precipitation of sphalerite starts. The main removal of Zn from the fluid system occurs at lower temperatures. Similarly, melt and fluid inclusion concentrations of many other trace elements directly reflect the crystallization and precipitation history of minerals at distinctive temperatures or temperature windows.     

Potential future changes in the characteristics of daily precipitation in Europe simulated by the HIRHAM regional climate model

In this study the potential future changes in various aspects of daily precipitation events over Europe as a consequence of the anticipated future increase in the atmospheric greenhouse gas concentrations are investigated. This is done by comparing two 3-member ensembles of simulations with the HIRHAM regional climate model for the period 1961–1990 and 2071–2100, respectively. Daily precipitation events are characterized by their frequency and intensity, and heavy precipitation events are described via 30-year return levels of daily precipitation. Further, extended periods with and without rainfall (wet and dry spells) are studied, considering their frequency and length as well as the average and extreme amounts of precipitation accumulated during wet spells, the latter again described via 30-year return levels. The simulations show marked changes in the characteristics of daily precipitation in Europe due to the anticipated greenhouse warming. In winter, for instance, the frequency of wet days is enhanced over most of the European continent except for the region on the Norwegian west coast and the Mediterranean region. The changes in the intensity and the 30-year return level of daily precipitation are characterized by a similar pattern except for central Europe with a tendency of decreased 30-year return levels and increased precipitation intensity. In summer, on the other hand, the frequency of wet days is decreased over most of Europe except for northern Scandinavia and the Baltic Sea region. In contrast, the precipitation intensity and the 30-year return level of daily precipitation are increased over entire Scandinavia, central and eastern Europe. The changes in the 30-year return level of daily precipitation are generally stronger than the corresponding changes in the precipitation intensity but can have opposite signs in some regions. Also the distribution of wet days is changed in the future. During summer, for instance, both the frequency and the length of dry spells are substantially increased over most of the European continent except for the Iberian Peninsula. The frequency and the length of wet spells, on the other hand, are generally reduced during summer and increased during winter, again, with the exception of the Iberian Peninsula. The future changes in the frequency of wet days in winter are related to a change in the large-scale flow over the North Atlantic and a corresponding shift of the North Atlantic storm track. The reduction in the frequency of wet days in summer is related to a northward extension of the dry subtropical region in the future, with a reduction of the convective activity because of the large-scale sinking motion in the downward branch of the Hadley cell. Because the atmosphere contains more moisture in the warmer future climate, the amount of precipitation associated with individual low-pressure systems or with individual convective events is increased, leading to a general increase in the intensity of individual precipitation events. Only in regions, where all the moisture evaporates from the ground already in spring, the intensity of precipitation events is reduced in summer.     

Doppler Shifts in the Quiet-Sun Transition Region and Corona Observed with Sumer on Soho

New observations of systematic red shifts of transition region and coronal lines obtained with SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on SOHO (the Solar and Heliospheric Observatory) are presented. With the extensive wavelength coverage of SUMER it is possible to extend the measurements of the red shifts to much higher temperatures compared to previous instruments. We find lines formed in the upper transition region (e.g. Ov, Sv, and Svi) to be red-shifted similar to lower temperature lines (T ≤ 1.8 x 10^-5 K). Even hotter lines such as Ovi, Neviii and Mgx show systematic red shifts on the order of 5 km s^-1 in the quiet Sun. This is a new and significant result since previous measurements of the red shifts were less well constrained. The behavior of the red shifts above T = 10^-5 K has been somewhat controversial. In some earlier investigations the magnitude of the red shift has been found to increase with temperature, reaching a maximum at T = 10^-5 K and then to decrease toward higher temperatures. Thus, our results will put new constraints on theoretical models. The measured shifts are compared to recent observations of red-shifted emission in stellar spectra obtained with the Hubble Space Telescope.     

Metallicity estimates for A-, F-, and G-type stars from the Edinburgh–Cape Blue Object Survey

The Edinburgh–Cape Blue Object Survey is an ongoing project to identify and analyse a large sample of hot stars selected initially on the basis of photographic colours (down to a magnitude limit     over the entire high-Galactic-latitude southern sky, and then studied with broad-band UBV photometry and medium-resolution spectroscopy. Due to unavoidable errors in the initial candidate selection, stars that are likely metal-deficient dwarfs and giants of the halo and thick-disc populations are inadvertently included, yet are of interest in their own right. In this paper we discuss a total of 206 candidate metal-deficient dwarfs, subgiants, giants, and horizontal-branch stars with photoelectric colours redder than     and with available spectroscopy. Radial velocities, accurate to ∼10–15 km s⁻¹, are presented for all of these stars. Spectroscopic metallicity estimates for these stars are obtained using a recently recalibrated relation between Ca  ii K-line strength and     colour. The identification of metal-poor stars from this colour-selection technique is remarkably efficient, and competitive with previous survey methods. An additional sample of 186 EC stars with photoelectric colours in the range     composed primarily of field horizontal-branch stars and other, higher gravity, A- and B-type stars, is also analysed. Estimates of the physical parameters T _eff, log  g , and [Fe/H] are obtained for cooler members of this subsample, and a number of candidate RR Lyrae variables are identified.