Rainfall-related debris flows in Carhuacocha Valley, Cordillera Huayhuash, Peru

Continuous heavy rainfall hit northern Peru in the second half of the 2008/2009 summer season. From the end of January to the beginning of March, the Cordillera Huayhuash experienced abnormally high precipitations that exceeded 270?mm. The antecedent rainfall, aggravated with a severe rainstorm of 20?mm on March 7 triggered a large debris flow in the upper Carhuacocha Valley early in the morning on March 8. The debris flow interrupted drainage from the upper part of the valley damming a lake in the narrow depression between the trough slope and the lateral moraine. As a result of the drainage interruption, water percolated through the moraine dam of Cangrajanca Lake where a secondary mass movement occurred in its inner slope. In September 2009, we mapped the debris flow and related landforms and estimated the total area and volume of both mass movements using geodetic measurements. About 104,000?m³ of sediments was moved from the trough slope towards the moraine from which 534,000?m³ flowed to Cangrajanca Lake subsequently. We analysed the rainfall conditions that triggered the debris flow using rainfall data from the nearby stations. We also compared the precipitation preceding the event with the rainfall thresholds for debris flow initiation.     

Binary Star Detection with the GAIA Radial Velocity Spectrometer

Accuracy of the radial velocities and efficiency of the spectroscopic binary detection with the GAIA radial velocity spectrometer (RVS) is evaluated by employing the observed spectra (Cenarro et al., 2001) and simulated GAIA observations. Evaluation is performed in the magnitude range V =10-17 by applying the cross-correlation method. This revised version was published online in July 2006 with corrections to the Cover Date.     

Hydrocarbon reservoir characterization of “AY” field,deep-water Niger Delta using 3D seismic and well logs

Three-dimensional seismic and well log data from nine wells were used for the characterization of “AY” field in the deep-water, Niger Delta. Result shows that the field has a complex structural arrangement consisting of series of northeast-southwest-trending and northwest-dipping synthetic faults. Petrophysical evaluation of the available well logs helped in identifying 11 hydrocarbon-bearing sands noted as A1000, A1100, A1200, A2000, B2000, B2100, C3000, C3100, D4000, D4100, and E5000. Reservoirs A1000, A1100, A1200, A2000, B2000, C3000, and D4000 are gas-bearing sands while reservoirs B2100, C3100, D4100, and E5000 are oil bearing. The average effective porosity of these reservoirs ranges from 0.168 to 0.292; water saturation is estimated to be between 0.177 and 0.59 and net-to-gross (NTG) ratio from 0.081 to 0.734. Considering the uncertainty in the input petrophysical parameters as well as structural uncertainty particularly in fluid contact, the total hydrocarbon reserves in the field were estimated to vary between 266.942 and 334.457 Bscf and 132.612 and 150.036 MMbbl for gas and oil volumes, respectively.     

The use of multivariate statistical analysis in the assessment of groundwater hydrochemistry in some parts of southwestern Nigeria

Arabian Journal of Geosciences - Turabah area is located in the southwestern Arabian Shield of Saudi Arabia. The present study aims to shed light on the origin and mechanism of formation of the...     

Der Exponentn in Suttons Ansatz für die lagrangesche Korrelationsfunktion

Zusammenfassung Der meteorologische Exponentn inO. G. Suttons Ansatz für dieLagrangesche Korrelationsfunktion kann nachSutton aus dem vertikalen Windprofil bestimmt werden, sofern dieses durch eine Potenzfunktion darstellbar ist. Im Falle gelten.Die vorliegende Untersuchung ergibt, daß bei genügender Luftbewegung das vertikale Windprofil in einer Luftschicht der Größenordnung 10² m durch (z) = (z₀) · (z/z₀)^m mit höhenkonstantemm hinreichend genau möglich ist. Eine Überprüfung derSuttonschen Bestimmungsvorschrift fürn ergibt hingegen, daß letztere im Hinblick auf das verwendete Mischungswegkonzept einer Korrektur bedarf.Die neue Bestimmungsvorschrift fürn hat die einfache Formn=m. Dieses Ergebnis wird durch experimentell ermittelte Daten gestützt.Für 0<m<1 istn<n (Sutton). Die Differenzn (Sutton)–n erreicht bei mittleren stabilen Schichtungsverhältnissen ihr Maximum. Dies wirkt sich u. a. bei der Bestimmung von Schornstein-Mindesthöhen mit Hilfe der Beziehung (1) dahingehend aus, daß die für den Fall stabiler Schichtung mitm=0,6 neu berechneten Schornsteinhöhen um etwa 7 bis 10% kleiner ausfallen als die mitn (Sutton) ermittelten.

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Summary The exponentn inO. G. Sutton's formula for the Lagrangian correlation functionR (), used in the statistical theory of turbulence, may be determined from the vertical wind profile provided the latter is given in the form of a power law i. e. (z) ~ z^m. AfterSutton the relationn=2m/(1+m) must hold. It is shown that this relation has to be put in the formn=m in order to avoid some inconsistencies inSutton's treatment. The theoretical considerations are in good agreement with experimental results obtained by different authors.

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Résumé SelonSutton, l'exposantn qui figure dans sa propre évaluation de la fonction de corrélation de Lagrange peut se déterminer à partir du profil de vent pour autant que celui-ci possède un potentiel de vitesse. La présente étude établit une certaine fonction pour ce profil dans une couche d'un hectomètre d'épaisseur environ. L'exposantn deSutton doit alors subir une correction. Il en résulte, entre autres, que pour une stratification stable de l'air le calcul d'une cheminée d'usine fournit une hauteur de 7 à 10% plus petite.

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Age et croissance de la truite lacustre (Salmo trutta lacustris L.) du Léman

The age and growth of adult Lake Geneva trout (Salmo trutta lacustris L.) caught from 1964 to 1974 for mark-and-recapture experiments was studied by scale analysis. The median lengths of 3 years and older fish were fitted to Von Bertalanffy growth curves. Their growth rates are higher than those of the fish younger than 3 years. It is conculded that this increase of growth rate concides with beginning of life in the lake, after the downstream migration of the juvenile trout which probably takes place in the second and third summer. No general increase of growth rates between cohorts could be detected from the beginning to the end of the period studied, in spite of a serious increase of eutrophication of Lake Geneva during the same time.      

The global distribution of long-term total ozone variations during the period 1957–1975

Total ozone observations in the international network have been used as a basis for the analysis of the mean monthly ozone distribution over the globe for the period 1957–75. It has been found that during the period 1961–70 the total ozone amount increased in the Northern Hemisphere by about 12 percent and that this increase seems to be significant at all latitudes. Although the data were sparse for the Southern Hemisphere, there did not appear to be any significant ozone changes during the 10 year period. Relatively large geographic variations were found in the ozone trends and it is suggested that these variations are related to large scale changes in the atmospheric circular pattern.