Phosphorus accumulation rates in metalliferous sediments on the East Pacific Rise

Based on phosphorus, iron and manganese analyses in 16 cores (5 dated) from the crest and flanks of the East Pacific Rise and the Bauer Deep we estimate that phosphorus is being deposited about 20 times faster in metalliferous sediments near the rise crest than in adjacent flank deposits, and about 40 times faster on the crest than in the Bauer Deep. Almost all of the phosphorus on the rise crest is contained in poorly crystallized hydrothermal iron oxyhydroxides, supporting Berner's (1973) proposal of phosphate sorption by these phases. The phosphate is probably derived from seawater, but some hydrothermal contribution cannot be excluded at this time. Flux estimates indicate that metalliferous sedimentation could remove 15–40% of the pre-agricultural river input of dissolved phosphate.     

A generalized continuum method for dynamic analysis of asymmetric tall buildings

The paper presents a continuum method for dynamic analysis of asymmetric tall buildings with uniform cross-section in which the horizontal stiffness is provided by shear walls and columns of arbitrary shape and layout, coupled by horizontal beams. The equations of motions are formulated in variational terms, including axial strain energy. Numerical solutions, obtained by using finite time differences and infinite polynomials, are presented for the response of a twenty-storey building with six shear walls to an impact load and earthquake accelerations. It is shown that omission of the axial deformations results in a substantially distorted pattern of behaviour, some of its effects being:

• 1 Overestimation of the bending stiffness of the coupled shear walls, with corresponding changes in their stiffness ratios.
• 2 Underestimation of the periods of the principal modes, with a corresponding change in the dynamic response.
• 3 Distortion of the magnitude, form, time of onset and coupling of the maximum displacements.
• 4 Pronounced change in the shear force and moment diagrams for the shear walls, the beams and the building as a whole.

     

APPLICATION OF A HILBERT TRANSFORM METHOD TO THE INTERPRETATION OF SURFACE-VEHICLE MAGNETIC DATA*

The development of an alkali vapour vehicle borne magnetometer providing very high resolution and a high sampling rate has called for reconsideration of interpretation procedures. With continuous profiling at ground level, the close proximity to near surface structures requires that the precise interpretation of geological boundaries be of paramount importance. Rapid digital recording also demands efficient data processing. Both these requirements can be met by the method described. Essentially the method reduces to a simple Hilbert transform of the magnetic profile. The calculation provides an extremely well defined position of the contact and accurate specification of the dip, strike, depth of overburden, and magnetic susceptibility parameters. Particular advantages are tolerance to high frequency noise, independence from a predetermined origin and baseline, and freedom from subjective judgements.     

Reply to comments by K.A. Goettel and J.S. Lewis

Uranium has been measured by homogenized fission track analysis in 34 samples of 22 achondrites. Potassium has been determined in aliquots of eleven of these. The results, combined with previous Al data, are not compatible with achondrite formation from chondritic material by previously suggested fractional melting or metal-sulfide segregation processes.     

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Ohne Zusammenfassung     

MINI-SOSIE FOR LAND SEISMOLOGY*

Mini-sosie consists in using a vibration-rammer as seismic source and changing the striking rate by varying the engine speed, resulting in a random impulse transmission. The recording instruments are made up of two seismic traces, two constant gain amplifiers and a two-channel sosie processor which performs the decoding in real time by using the actual transmission times supplied by a captor located on top of the vibration-rammer's plate. An idea of the possible penetration is given by the recording of a velocity survey. Other results obtained in seismic reflection and refraction are given.     

Application of Geophysical Techniques in Identifying UNE Signatures at Semipalatinsk Test Site (for OSI Purposes)

This article describes geological and geophysical studies of an underground nuclear explosion area in one of the boreholes at the Semipalatinsk test site in Kazakhstan. During these studies, the typical elements of mechanical impact of the underground explosion on the host medium—fracturing of rock, spall zones, faults, cracks, etc., were observed. This information supplements to the database of underground nuclear explosion phenomenology and can be applied in fulfilling on-site inspection tasks under the Comprehensive Nuclear-Test-Ban Treaty.     

Surface Energy Exchanges during Pre-monsoon Thunderstorm Activity over a Tropical Station Kharagpur

In the present study an attempt has been made to understand the variation of surface energy fluxes such as net radiation, sensible, latent and soil heat during different epochs of thunderstorm activity at Kharagpur. The study also focuses in delineating the difference in the surface energy budget from the days of thunderstorm activity to fair weather days in the pre-monsoon months (April and May) which is locally known as thunderstorm season. For this purpose, experimental data obtained from the Severe Thunderstorms- Observations and Regional Modeling (STORM) programme during pre-monsoon months of 2007, 2009 and 2010 at Kharagpur (22°30′N, 87°20′E), West Bengal, India are used. The present study reveals quick response, in the order of a few days, in the variations of transport of energy fluxes at soil-atmosphere interface to the upper atmosphere vis-à-vis to the occurrence of thunderstorm activity. Rise of surface sensible heat flux to the level of surface latent heat flux a day or two before the occurrence of a thunderstorm has been identified as a precursor signal for the thunderstorm occurrence over Kharagpur. Distinguishable differences are found in the partitioning of the surface energy fluxes to that of net radiation between thunderstorm and non-thunderstorm days. The present study reveals more Bowen’s ratio during thunderstorm days to that of nonthunderstorm days. These results are useful in validating mesoscale model simulations of thunderstorm activity.     

Fractional Tajimi–Kanai model for simulating earthquake ground motion

The ground acceleration is usually modeled as a filtered Gaussian process. The most common model is a Tajimi–Kanai (TK) filter that is a viscoelastic Kelvin–Voigt unit (a spring in parallel with a dashpot) carrying a mass excited by a white noise (acceleration at the bedrock). Based upon the observation that every real material exhibits a power law trend in the creep test, in this paper it is proposed the substitution of the purely viscous element in the Kelvin Voigt element with the so called springpot that is an element having an intermediate behavior between purely elastic (spring) and purely viscous (dashpot) behavior ruled by fractional operator. With this choice two main goals are reached: (i) The viscoelastic behavior of the ground may be simply characterized by performing the creep (or the relaxation) test on a specimen of the ground at the given site; (ii) The number of zero crossing of the absolute acceleration at the free field that for the classical TK model is \(\infty \) for a true white noise acceleration, remains finite for the proposed model.     

Water relation characteristics ofAlhagi sparsifolia and consequences for a sustainable management

Water relation characteristics of the desert legumeAlhagi sparsifolia were investigated during the vegetation period from April to September 1999 in the foreland of Qira oasis at the southern fringe of the Taklamakan Desert, Xinjiang Uygur Autonomous Region of China. The seasonal variation of predawn water potentials and of diurnal water potential indicated thatAlhagi plants were well water supplied over the entire vegetation period. Decreasing values in the summer months were probably attributed to increasing temperatures and irradiation and therefore a higher evapotranspirative demand. Data from pressure-volume analysis confirmed thatAlhagi plants were not drought stressed and xylem sap flow measurements indicated thatAlhagi plants used large amounts of water during the summer months. Flood irrigation had no influence on water relations inAlhagi probably becauseAlhagi plants produced only few fine roots in the upper soil layers. The data indicate thatAlhagi sparsifolia is a drought-avoiding species that utilizes ground water by a deep roots system, which is the key characteristic to adjust the hyper-arid environment. Because growth and survival ofAlhagi depends on ground water supply, it is important that variations of ground water depth are kept to a minimum. The study will provide a theoretical basis for the restoration and management of natural vegetation around oasis in arid regions.