A synthetic model for daily streamflow

This paper presents a model for synthesising daily average streamflow data that is suitable for most rivers in Great Britain. The method is based on a linear interpolation of the logorithms of 5-day average flows. The 5-day average flows are produced using N.T. Kottegoda's statistical model (Thesis, Univ. of Birmingham, 1970). The 5-day model preserves the long-term statistical characteristics of the daily data, while the short-term characteristics such as hydrograph shape are imposed by the interpolation method.

A stochastic error term is superimposed on the interpolated daily flows. This term represents the non-deterministic component of the daily time series. The analysis of the observed error terms represents an important part of this paper.

The riverflow in the Severn at Bewdley is used to demonstrate both the analysis of actual data and the generation of synthetic data. The technique is then applied to data from two other rivers with widely differing characteristics to demonstrate the range of the method.     

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.     

Magma mixing in mafic alkaline volcanic rocks: the evidence from relict phenocryst phases and other inclusions

Green clinopyroxenes, commonly rounded and anhedral and richer in Fe, Na and Mn than the pyroxenes of the surrounding groundmass are a common feature of mafic alkaline volcanic rocks (e.g. basanites, monchiquites, leucitites). Some are accompanied by one or more of the following phases: Fe-rich kaersutite and biotite, anorthoclase, sodic plagioclase, apatite, magnetite, sphene, which are believed to be cognate with the green pyroxenes. We review evidence that these minerals have crystallized from mugearite, trachyte or phonolite magmas, and their presence in mafic alkaline rocks is due to magma mixing. The intermediate and salic magmas may sometimes be generated at mantle depths, possibly by melting of mantle material enriched in Fe, Na and volatiles.     

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.