Compressional angles of isallo stress theory for a circular-cylindrical,spherical and elliptic-cylindrical elastic inhomogeneity in an elastic medium

Summary The compressional angle of isallo stress theory for the case of a cylindrical (circular and elliptic) and spherical subsurface inhomogeneity, assuming that the conjugate fracture surfaces are inclined at a Mohr angle of 30° toward the largest compression, has been calculated. The solution for a spherical and cylindrical inclusion in an infinite medium subject to a uniform stress field (at infinity) were taken as the basis for the stress analysis. The stress angle was then calculated for the mentioned types of inclusions.     

Gleichzeitige Messungen des Seegangs mit nicht-stabilisierten Beschleunigungsschreibern an Orten mit unterschiedlicher Wassertiefe in der Deutschen Bucht

Zusammenfassung Es werden Ergebnisse von simultanen Seegangsmessungen an sieben Pl?tzen mit verschiedener Wassertiefe im Küstengebiet der Deutschen Bucht behandelt. An Hand einiger Gegenüberstellungen wird dargelegt, in welcher Weise die Windsee mit abnehmender Wassertiefe niedriger und kürzer wird.

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Simultaneous measurements of waves by means of non-stabilized recording accelerometers at various places in the German Bight with different water depths

Summary Treated are the results of simultaneous measurements of waves at seven places in the coastal area of the German Bight with different water depths. A comparison demonstrates the way in which the wind sea is getting lower and shorter with decreasing water depth.

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Mesures simultanées de l'agitation de la mer avec accéléromètres enregistreurs non stabilisés en points de profondeurs différentes de la Baie Allemande

Résumé On a traité les résultats obtenus de mesures simultanées de l'agitation de la mer en sept endroits de profondeurs différentes dans les eaux c?tières de la Baie Allemande. En utilisant quelques comparaisons on expose de quelle manière la mer due au vent diminue de hauteur et de longueur en même temps que la profondeur.

     

Dünung und Windstau

Summary These remarks trie to explain the behaviour of local wind effect on the coast under the additional influence of swell approximately running parallel to the wind's direction. Owing to the high speed of long swell waves the wind's tangential shearing strain on the water masses may become less effective than it would do if no coincidence with swell waves would occur.

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La houle et l'effet local du vent

Résumé Cet essai cherche à expliquer le comportement de l'effet local du vent sous l'influence additionnelle d'une houle qui suit approximativement la direction du vent. Par suite de la grande vitesse de propagation d'une longue houle, l'effet de cisaillement tangentiel que le vent exerce sur l'eau diminuera dans le cas où l'effet local du vent coincide avec le phénomène additionnel de la houle.

     

Über die DÜnung aus einem Windfeld,welches am Beobachtungsort in einiger Entfernung vorbeizieht

Zusammenfassung Es werden die zum Teil recht verwickelten Bedingungen besprochen, denen eine am festen BeobachtungsortA auftretende DÜnung genÜgt, wenn das wellenerzeugende Windfeld sich dem PunktA wohl nähert, an ihm dann aber in einiger Entfernung vorbeizieht. Es werden getrennt behandelt: 1. wandernde Windfelder, welche seit langer Zeit eine ausgereifte Windsee besitzen, 2. wandernde Windfelder, deren Ausbildung erst kÜrzere Zeit zurÜckliegt.An geeigneter Stelle wird ein Diagramm gegeben, welches die Bestimmung der angular spreading factors (W. J. Pierson jun., G. Neumann und R. W. James [1953]) wesentlich erleichtert.Abschließend wird die Frage erörtert, ob ein Punkt am Rande des Windfeldes den gesamten Windfeld-Leerand ausreichend repräsentieren kann.

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On swell generated by a fetch passing at some distance from the observation point

Summary The paper treats the rather complex conditions that may lead to the occurrence of swell at a fixed observation pointA when the wave generating fetch though approaching pointA passes it at some distance. Two contingencies are separately discussed: 1) moving fetches associated for a long time past with a fully developed wind sea, 2) moving fetches whose generation took place only quite recently.The paper includes a diagram which largely facilitates the determination of the angular spreading factor (W. J. Pierson jun., G. Neumann, and R. W. James [1953]).In the end, the question is discussed whether one point on the border of the fetch may be regarded as being sufficiently representative of the entire lee-side of the fetch.

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Sur une houle soulevée par un »fetch« qui passe le point d'observation à quelque distance

Résumé Ce travail traite les conditions assez complexes qui peuvent conduire à l'apparition de houles à un point fixe d'observationA si le »fetch« qui a soulevé les vagues en question s'approche de ce point mais finit par le passer à quelque distance. On discute deux éventualités: 1) des »fetches« progressifs dont les vagues de vent on depuis longtemps terminé leur developpement, 2) des »fetches« progressifs qui n'ont accompli leur formation que depuis peu.On a introduit dans le travail un diagramme qui rend beaucoup plus facile la détermination des facteurs d'extension angulaire (»angular spreading factors«) (W. J. Pierson, jun., G. Neumann et R. W. James [1953]).Enfin, on discute la question si un seul point sur le bord du »fetch« peut suffisamment représenter les conditions dominant sur tout le bord sous le vent.

     

Ergebnisse von Messungen heutiger Krustenbewegungen

Ohne Zusammenfassung     

Effects of groundwater flow on mineral diagenesis, with emphasis on carbonate aquifers

 This article provides a critical synopsis of the effects of groundwater flow on mineral diagenesis. Emphasis is placed on those aspects and processes that change porosity and permeability in carbonate aquifers, because they are of particular importance to human societies as sources of supplies of water for human consumption (drinking, irrigation) and of crude oil and natural gas. Diagenetic settings in carbonates as well as clastics are generally ill defined. This paper proposes a new comprehensive classification of diagenetic settings into near-surface, shallow-, intermediate-, and deep-burial diagenetic settings; hydrocarbon-contaminated plumes; and fractures. These settings are defined on the basis of mineralogy, petroleum, hydrogeochemistry, and hydrogeology. This classification is applicable to all sedimentary basins. Diagenesis is governed by various intrinsic and extrinsic factors that include thermodynamic and kinetic constraints, as well as microstructural factors that may override the others. These factors govern diagenetic processes, such as dissolution, compaction, recrystallization, replacement, and sulfate–hydrocarbon redox-reactions. Processes such as cementation, dissolution, and dolomitization require significant flow of groundwater driven by an externally imposed hydraulic gradient. Other processes, such as stylolitization and thermochemical sulfate reduction, commonly take place without significant groundwater flow in hydrologically nearly or completely stagnant systems that are geochemically "closed." Two major effects of groundwater flow on mineral diagenesis are enhancement and reduction of porosity and permeability, although groundwater flow can also leave these rock properties essentially unchanged. In extreme cases, an aquifer or hydrocarbon reservoir rock can have highly enhanced porosity and permeability due to extensive mineral dissolution, or it can be plugged up due to extensive mineral precipitation. Received, April 1998 · Revised, July 1998 · Accepted, September 1998     

Nonlinear wave coupling in type IV solar radio bursts

In order to explain a fine structure of parallel ridges in stationary type IV continua, the emission due to the coupling of electrostatic upper hybrid waves and Bernstein waves at the sum frequency of the upper hybrid and harmonics of the gyro frequency has been calculated. If the energy density of these electrostatic waves is of the order of 10^-3 times the thermal energy density, then the observed zebra pattern can be emitted by a region with a diameter of 10³ km.