Der physikalische Zusammenhang zwischen der statischen Abplattung und dem inneren Aufbau der Erde auf der hypothetischen Grundlage einer sechsparametrigen Gleichgewichtsfigur

Zusammenfassung Es wird eine allgemeine Theorie der mehrparametrigen Gleichgewichtsfiguren entwickelt. Die Gleichgewichtsbedingung wird folgendermaßen formuliert: 1. Das Dichtegesetz ist streng individuell. 2. Jede Gleichgewichtsfigur besteht aus mehreren, durch Diskontinuitätsflächen getrennten Teilen, deren jeder das Dichtegesetz der einparametrigen Gleichgewichtsfiguren aufweist oder homogen ist. 3. Bei Entblätterung der Figur bis zur innersten Diskontinuitätsfläche resultiert ein null oder einparametriger Kern. Für das Normalsphäroid der Erde wird ein dreiteiliges Modell zugrundegelegt, bestehend aus einer homogenen Wasserhülle, einem heterogenen Mantel und einem ebensolchen Kern. Nach Abhebung des Ozeans verbleibt eine vierparametrige Festerde, wobei die Kernoberfläche in 2900 km Tiefe angenommen wird. Da zur eindeutigen Lösung zwei Bestimmungsstücke fehlen, erhält man ² Lösungen, deren Gültigkeitsbereich durch drei lineare Reihen von Grenzfiguren abgeschlossen ist: eine Figurenreihe mit homogenem Kern und heterogenem Mantel, eine Reihe mit homogenem Mantel und heterogenem Kern und eine Reihe mit verschwindendem Dichtesprung an der Kernoberfläche. Die drei Ecken des Feldes sind durch folgende Figuren gegeben:a) einWiechert'sches Modell, bestehend aus einem homogenen Mantel und einem homogen Kern; diese Figur weist das maximale HauptträgheitsmomentC auf.b) die GrenzfigurB mit homogenem Kern und verschwindendem Dichtesprung, welche das minimale Trägheitsmoment hat.c) die GrenzfigurC mit homogenem Mantel und dem Dichtesprung Null. Innerhalb der empirischen Unsicherheit fällt das aus der dynamischen und statischen Abplattung der wirklichen Erde für die Festerde berechnete Hauptträgheitsmoment mit dem Minimalwert der FigurB zusammen. Es scheint demnach, daß die wirkliche Erde durch einen minimalen Drehimpuls ausgezeichnet ist, womit aber gleichzeitig der Kern homogen sein muß und an der Kernoberfläche kein Dichtesprung auftreten dürfte.

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Summary A general theory of multiparameter figures of equilibrium is developed. The condition of equilibrium is formulated as follows: 1. The density-law is strictly individual. 2. Each figure of equilibrium consists of several parts separated by surfaces of discontinuity, each of which has the density-law of the one parametric figures of equilibrium or is homogeneous. 3. Peeling off the figure to the lowest surface of discontinuity results a zero- or a one parametric core. For the normal spheroid of the earth a three-partite model consisting of a homogeneous water-cover, a heterogeneous mantle and of such a core is taken as basis. After peeling off the ocean a four-parametric solid earth remains, assuming the depth of the surface of the core in 2900 km. As for an unequivocal solution two data are lacking, we find ² solutions the domain of which is separated by three linear series of boundary-figures: a series of figures with homogeneous core and heterogeneous mantle, a series of figures with homogeneous mantle and heterogeneous core and a series with vanishing difference of density on the surface of the core. The three corner points of this field are represented by following figures:a) aWiechert-model consisting of a homogeneous mantle and a homogeneous core; this figure has the maximum of moment of inertiaC. b) the boundary figureB with homogeneous core and vanishing difference of densities, which has the minimum ofC. c) the boundary figure with homogeneous mantle and also vanishing difference of densities on the surface of the core. Within the empirical uncertainty the moment of inertiaC calculated from the dynamic and static flattening of the real earth coincides with the minimum value of figureB. Therefore it seems that the real earth is distincted by the minimum moment of rotation, in which case simultaneously the core must be homogeneous and the difference of density on the core's surface must vanish.

     

地下水位变化引起地面形变的可能机理

本文主要探讨了对承压水层上的单井,以定流量 Q 抽水时造成地面形变的可能机理.抽水形成了降落漏斗,漏斗区域内的动水压力降低导致了水层的沉降,这就等于给水层上的盖层施加了一个横向分布的载荷.若把覆盖层看做一个弹性薄板,因而计算出抽水引起的地面垂直形变、水平形变及附加应力等量值.     

Impact des crues sur les bilans sédimentaires de chenaux secondaires de la Loire moyenne (France)

Volumes of sediments eroded and deposited during floods were quantified in a vegetated secondary channel of the Loire River at the study site of Bréhémont (France). The topographic survey highlights the temporal variability in filling of secondary channels. Upstream riffle of secondary channels governs sedimentary supply. In these channels, sediments show a by-passing in the lower parts and an accretion in the higher vegetated areas. The asymmetrical morphology is reinforced during both intense and moderate floods. Sedimentary accretion in the vegetated areas leads progressively to channel narrowing. To cite this article: S. Rodrigues et al., C. R. Geoscience 337 (2005).     

A luminescence‐based chronology for the Harletz loess sequence,Bulgaria

The Harletz loess‐palaeosol sequence is located in northwestern Bulgaria and represents an important link between well‐studied loess sequences in eastern Romania and further sites to the west of the Carpathians (e.g. Serbia and Hungary). The aim of this study was to establish a chronostratigraphy of the deposits, using various methods of luminescence dating, together with basic stratigraphical field observations as well as magnetic properties. Luminescence dating was carried out using the quartz fine grain fraction and a SAR protocol, and the feldspar coarse grain fraction, applying the MET‐pIRIR protocol. Due to underestimation of the quartz fine grain fraction in the lower parts of the sequence, the resulting chronology is mainly based on the feldspar ages, which are derived from the stimulation temperature at 150 °C. A comparison with nearby sequences from Serbia, Hungary and Romania, and interpretations obtained through the stratigraphical and sedimentological signature of the sequence, supports the established chronology. Our data suggest that the prominent palaeosol (soil complex) in the upper quarter of the sequence was formed during MIS 5. It would follow that large parts of the Last Glacial loess overlying this palaeosol were probably eroded, and that the thick loess accumulation underlying this soil complex can be allocated to the penultimate glacial (MIS 6). A prominent MIS 6 tephra, which has been reported from other sequences in the area, is also present at Harletz.     

Length Scales of Scalar Diffusion in the Convective Boundary Layer: Laboratory Observations

A laboratory study of scalar diffusion in the convective boundary layer has found results that are consistent with a 1999 large-eddy simulation (LES) study by Jonker, Duynkerke and Cuijpers. For bottom-up and top-down scalars (introduced as ‘infinite’ area sources of passive tracer at the surface and inversion, respectively) the dominant length scale was found to be much larger than the length scale for density fluctuations, the latter being equal to the boundary-layer depth h. The variance of the normalized passive scalar grew continuously with time and its magnitude was about 3–5 times larger for the top-down case than for the bottom-up case. The vertical profiles of the normalized passive scalar variance were found to be approximately constant through the convective boundary layer (CBL) with a value of about 3–8c_*² for bottom-up and 10–50c_*² for top-down diffusion. Finally, there was some evidence of a minimum in the variance and dominant length scale for scalar flux ratios (top-down to bottom-up flux) close to −0.5. All these convection tank results confirm the LES results and support the hypothesis that there is a distinct difference in behaviour between the dynamic and passive variables in the CBL.     

华南、华北地块中生代构造演化与超高压变质岩的折返机制

本文在讨论中国东部现有构造演化模式基础上，着重从华北与华南地块之间板块尺度的动力学过程剖析秦岭－大别中生代造山带构造演化，以及大别－苏鲁超高压变质地体的形成和折返过程。晚二叠世－中三叠世华南地块向华北地块持续挤压，陆壳大规模俯冲导致超高压变质作用的产生，而华北地块在晚三叠世至早侏罗世发生快速逆时针旋转，使得这一地区上地幔深度的超高压变质地体快速折返至下地壳。由于超高压变质地体侵位后，地壳结构、构造的差异，在南北地块的进一步挤压下，造成中国东部晚侏罗世－早白垩世郯庐断裂带的巨大左行剪切。     

Fragmentation Energy in Rock Blasting

The theoretical explosive energy used in blasting is a common issue in many recent research works (Spathis 1999; Sanchidrian 2003). It is currently admitted that the theoretical available energy of the explosives is split into several parts during a blast: seismic, kinetic, backbreaks, heave, heat and fragmentation energies. Concerning this last one, the energy devoted to the breakage and to the creation of blocks within the muckpile can be separated from the microcracking energy which is devoted to developing new and/or extending existing micro cracks within the blocks (Hamdi et al. 2001; López et al. 2002). In order to investigate these two types of energy, a first and important task is to precisely study the main parameters characterising the two constitutive elements of the rock mass (rock matrix and discontinuity system). This should provide useful guidelines for the choice of the blasting parameters (type of explosive, blasting pattern, etc.), in order to finally control the comminution process. Within the frame of the EU LESS FINES research project, devoted to the control of fines production, the methodology was developed in order to: (1) characterize the in situ rock mass, by evaluating the density, anisotropy, interconnectivity and fractal dimension of the discontinuity system and (2) evaluate fragmentation (both micro and macro) energy spent during the blasting operation. The methodology was applied to three production blasts performed in the Klinthagen quarry (Sweden) allowing to estimate the part of the fragmentation energy devoted to the formation of muck pile blocks on one side and to the muckpile blocks microcracking on the other side.     

Environmental controls on the Late Holocene carbonate sedimentation of a karstic lake in the Middle‐Atlas Mountains (Lake Afourgagh,Morocco)

The Lake Afourgagh sediment record and facies successions provide an outstanding example of environmentally controlled carbonate sedimentation. Afourgagh is a small, shallow permanent lake located in the Middle‐Atlas Mountains in Morocco in a karstic context. It is fed by ground waters that are relatively enriched in Mg resulting from the leaching of the Jurassic dolomitic bedrock of the catchment. This eutrophic lake is episodically restricted and characterized by alkaline waters with a fluctuating high Mg/Ca ratio. The maximum extension of the Holocene shoreline coincides with evidence of a lake stabilization level corresponding to the outflow of the lake through a wadi. Lakeshore terrace sediments deposited on an alluvial fan siltstone during the past ca 2500 cal yr bp comprise four main facies: a littoral crust, palaeosols, palustrine silts and charophyte tufas, which reflect different environments from the shoreline toward the deeper water. In the more distal parts, the charophyte tufas display a well‐expressed lamination punctuated by the development of microstromatolites on algae thalli. The mineralogical composition of the carbonates is linked to the facies. While the charophyte tufas are characterized by a relatively high content in aragonite, in addition to low‐Mg calcite, the littoral crust is mainly composed of magnesite. This pattern is related to the evolving chemistry of water due to the influence of charophyte proliferation during dry summers. Calcium‐carbonate precipitation on algae thalli (both bioinduced and microbially mediated) progressively induces an increase in the Mg/Ca ratio of the lake water, while the capillary evaporation of shallow ground waters causes precipitation of a magnesite precursor on the shoreline, producing magnesite during early diagenesis. This effect is characteristic of two episodes: part of the Roman Warm Period and the beginning of the Dark Age Cold Period. The carbonate mineralogy of the different depositional sequences at Afourgagh indicates lake‐level and water‐chemistry fluctuations under a climatic influence. Therefore, among other regional records, the Lake Afourgagh sedimentary record provides useful evidence for reconstructing these environmental changes.