Universidad National de La Plata Museo

Ohne Zusammenfassung     

Analysis of absorption effects on the dynamic response of dam reservoir systems by boundary element methods

Using reciprocal theorems for dynamic and static boundary value problems, boundary integral equations are presented for wave propagation in elastic, isotropic media and compressible, inviscid fluids in the time domain as well as in the frequency domain. For the analysis of fluid–soil and fluid–structure systems, suitable coupling conditions are prescribed along the interfaces. The numerical treatment of the boundary integral equations consists of a point collocation and of a discretization of the boundary, in which constant and linear approximation functions are assumed. Step-by-step integration is applied to the time-dependent equations, where again the states are taken to be linear and constant over each time interval. These boundary element procedures are used to analyse the response of dams due to horizontal and vertical ground motions considering dam–water interaction and absorption of hydrodynamic pressure waves at the reservoir bottom or at the far end into the soil medium. Both the frequency response and the impulse generated transient response are investigated.     

Attenuation of high-frequency earthquake waves in South America

Earlier attenuation studies for the South American continent indicate that for Sn and Lg waves there is low attenuation in the shield region east of the Andes, whereas in the west of South America, with some exceptions, there is high attenuation. Those studies, however, were nonquantitative. In this study theQ ₀ (1-Hz values) for Lg waves for South America are presented, based on a scattering model ofAki (1969) as extended byHerrmann (1980) for the coda waves of shallow local and near-regional earthquakes. The results of the codaQ method are compared with those obtained byNuttli's method (1973). TheseQ ₀ values are in good agreement with the apparentQ ₀ of Lg waves obtained by the latter method. The data were obtained from over 100 local and regional earthquakes recorded by 12 WWSSN stations throughout continental South America. They provided a range of frequencies from 0.4 to 1.4 Hz, for which the frequency dependence ofQ was investigated by assumingQ=Q ₀(f/f ₀). The observed data indicate that the tectonic region of western South America is characterized by lowQ ₀ and a large frequency-dependent factor , the values ranging from 150 to 350 and 0.4 to 0.7, respectively. TheQ ₀ values increase in the shield region east of the Andes, but frequency dependence decreases. The average crustalQ ₀ for north and central Argentina ranges from 420 to 580, and ranges from 0.2 to 0.3. TheQ ₀ is larger in the Brazil region, ranging from 580 to 980, and varies from 0.0 to 0.2. In the lower-attenuation region of eastern South America higher values of attenuation correlate with greater thickness of the sedimentary layers.     

Identification of bicyclic terpenoid hydrocarbons in the saturate fraction of Athabasca oil sand bitumen

The bicyclic terpanes reported to be present in numerous petroleums have been detected in the saturate fraction of the Athabasca oil sand bitumen. This series of compounds has been found to extend from C₁₅ to at least C₂₄ and their structures have been established by means of comparisons with synthetic C₁₈ and C₂₀ samples of known stereochemistry.     

Ground-motion modelling at regional distances for earthquakes in a continental interior,II. Effect of focal depth,azimuth and attenuation

Multiple-mode surface-wave signals are used to model ground motion at distances of 50 to 500 km for an earthquake source in a continental interior. Motion on a thrust fault is used as the earthquake model. Theoretical ground-motion time histories are generated for this source for various focal depths, receiver azimuths and medium-attenuation models. A shallow source will generate greater values for the ground motion than the same source at a greater depth. Two anelastic attenuation models are considered, one appropriate to the central and eastern United States and the other to southern California. The effects of the difference in the attenuation models are seen at distances greater than 100 km for periods greater than 1.5 sec.     

Der Nordrand des Tauernfensters zwischen Mayrhofen und Inner Schmirn (Tirol)

Zusammenfassung Der innerste Bereich des Tauernfensters kann als Helvet betrachtet werden. Hier findet sich auf dem voralpinen Kristallin oberjurassischer Hochstegenkalk, gefolgt von einer Serie mit Metaarkosen, Brekzien und Schiefern vermutlich kretazischen Alters. Es lassen sich dabei autochthone, parautochthone und allochthone Anteile unterscheiden. Von Süden her überschoben folgt darauf mit verkehrten und aufrechten Serien das penninische Deckensystem der Oberen Schieferhülle. Der Fensterrahmen wird von einer tektonischen Mischserie (Richbergkogelserie) sowie vom unterostalpinen Innsbrucker Quarzphyllit mit dem Tarntaler Mesozoikum gebildet, welch letzteres sich in drei Decken mit unterschiedlicher fazieller Ausbildung gliedern läßt.

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The lowermost structural elements exposed in the Tauern window can be taken for Helvetikum. Within this unit the crystalline socle is overlain by the Upper Jurassic Hochstegen limestone and a variegated series of meta-arkoses, breccias, and phyllites probably of Cretaceous age. Autochthonous, parautochthonous, and allochthonous elements can be distinguished. Thereupun follows the Penninic nappe system of the Obere Schieferhülle which displays inverted and normal rock sequences. The frame of the Tauern window is formed by a tectonically mixed series (Richbergkogel series) and the Lower East Alpine Innsbruck quartz phyllite with the Tarntal Mesozoic. The latter can be divided into three nappes.

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Résumé La domaine le plus interne de la fenêtre des Tauern peut être considéré comme relevant de l'Helveticum. Ici reposent d'abord sur le cristallin préalpin après un Jurassique inférieur rudimentaire, une épaisse sédimentation transgressive calcaire appartenant au Jurassique supérieur (calcaire de Hochstegen), suivie d'une série de métaarkoses, brèches et phyllites probablement d'âge crétacé. On peut y distinguer des parties autochthones et des parties parautochthones et allochthones.L'élément structural suivant, venu du sud, doit être consideré comme appartenant au Penninicum; c'est le système de nappes de 1'«Obere Schieferhülle», où on peut distinguer des séries renversées et normales.L'enveloppe de la fenêtre des Tauern comprend une série tectonique composite (série de Richbergkogel) ainsi que les Phyllades d'Innsbruck et les séries mésozoïques de la Tarntal.Dans ces dernières, on peut distinguer trois nappes: l'inférieure, celle de Torwand (ou Hippold), avec à la base, des phyllades paléozoïques, des sédiments rudimentaires triasiques, d'épaisses brèches posttriasiques, des radiolarites, et enfin des arkoses, grès et conglomérats avec composantes sporadiques de radiolarite. Au-dessus vient la nappe de Reckner avec des séries triasiques et jurassiques et des serpentinites. En haut se trouve une nappe (nappe de Möls) comprenant des sédiments rudimentaires mésozoïques et les Phyllades d'Innsbruck.

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