Universität Stuttgart
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Item Open Access Confirmation of siderazot, Fe3N1.33, the only terrestrial nitride mineral(2021) Bette, Sebastian; Theye, Thomas; Bernhardt, Heinz-Jürgen; Clark, William P.; Niewa, RainerSiderazot, the only terrestrial nitride mineral, was reported only once in 1876 to occur as coating on volcanic rocks in a fumarolic environment from Mt. Etna and, to date, has been neither confirmed nor structurally characterized. We have studied the holotype sample from the Natural History Museum, London, UK, originally collected by O. Silvestri in 1874, and present siderazot with epsilon-Fe3N-type crystal structure and composition of Fe3N1.33(7) according to crystal structure Rietveld refinements, in good agreement with electron microprobe analyses. Crystal structure data, chemical composition, and Raman and reflectance measurements are reported. Possible formation conditions are derived from composition and phase stability data according to synthetic samples.Item Open Access "A la recherche du temps perdu" : on geological condensation, with examples from the Jurassic Subbetic Plateau in Southeastern Spain(1993) Fels, Alexander; Seyfried, HartmutEine kondensierte Ablagerung ist eine marine Rückstandsbildung, die sich autochthon und kontinuierlich über einen längeren Zeitraum hinweg gebildet hat. Kondensation kann synsedimentar durch Abschirmung, Ablenkung oder Abtragung von Schlamm erfolgen; diagenetisch läuft Kondensation vor allem über Bioerosion auf Hartboden in Verbindung mit unterschiedlich tiefgreifender Erosion ab. Im Jura des subbetischen Plateaus (früher "externes Subbetikum") wird das Umkippen in eine Kondensations-Situation durch tektonische Bewegungen gesteuert, indem benachbarte Plattformen den Export von Schlamm selbssteuernd regulieren. Das subbetische Plateau durchlief vier Phasen stark reduzierter Sedimentation: Carixien - Unter-Domerien(Kondensatlonsepisode 1), Obertoarcien - Unter-Bajocien (Kondensationsepisode 2), Unterbathonien - Unter-Oxfordien (Kondensationsepisode 3) und unterstes Kimmeridgien (Kondensationsepisode 4). Hartboden, die sich während dieser Episoden bildeten, sind meistens von Goethitkrusten und Goethitonkoiden bedeckt. Die meisten Goethitkrusten bestehen entweder aus sehr dünnen (20 - 50 p.) Laminae mit krümeligem und pseudofilamentösem Gefüge, die für einen mikrobiellen Ursprung der Krusten sprechen, oder sie bestehen aus strukturlosem, "sterilen" Goethiterz. Aus einer Abschätzung der Wachstumsraten folgern wir, daß der überwiegende Teil der Zeit, die in solchen Krusten versteckt ist, entweder im nur wenige Milimeter dicken Goethiterz dokumentlert ist oder in Hartböden bzw. Erosionsflächen gelöscht wurde. Kondensierte Abfolgen zelgen meistens eine hierarchische Gliederung in Sequenzen, die vom Meter- bis zum Millimeterbereich reichen und nahezu stets denselben Aufbau haben: sie beginnen mit reduzierter Sedimentation, auf die ein Omissionsstadium folgt und schließen melstens mlt Goethitkrusten ab. Unter den vielen Faktoren, die für eine solche Abfolge verantwortlich sein konnen, kristallisiert sich als kleinster gemeinsamer Nenner ein (nicht eindeutig kalibrierbares) eustatisches Signal heraus. Wir betrachten deshalb kondensierte Sequenzen, die Goethitkrusten enthalten, als pelagische Parasequenzen.Item Open Access Item Open Access Boussinesq’s problem of viscoelasticity(1991) Wolf, DetlefWe consider an isochemical, isentropic, incompressible fluid half-space and study quasistatic viscoelastic perturbations, induced by two-dimensional (2D) surface loads, of a hydrostatic initial state. In view of the regional or local scale required for deformations of planets to be amenable to the half-space approximation, the model is assumed to be externally gravitating. We derive analytic solutions for the displacement and incremental stress components and study several approximations to the expressions. Particular emphasis is placed on discriminating between the material and local incremental stresses. Based on this distinction, deeper insight is gained into the physical significance of the solution.Item Open Access Glacial isostasy and long-term crustal movements in Fennoscandia with respect to lithospheric and asthenospheric processes and properties : comment(1991) Wolf, DetlefRecently, Mörner discussed his model of glacio-isostatic compensation in the light of new seismological models of the upper mantle below Fennoscandia. He concluded that the P-wave velocity distribution is in "full agreement" with his estimate of the viscosity distribution as inferred from glacio-isostatic relaxation. Whereas the consistency of seismological and geodynamical earth models is a necessary condition for their soundness, the particular type of agreement sought by Mörner is not required or expected, nor can his method of attaining such agreement be approved. For easier understanding of my criticism, I briefly recall the type of information provided by the seismological and by the glacio-isostatic evidence.Item Open Access Seismographen(1996) Wielandt, ErhardIm Heubachtal bei Schiltach im Schwarzwald, in einem alten Silberbergwerk 150 Meter unter Tage, stehen einige der empfindlichsten Seismographen Deutschlands. Wer allerdings meint, er könne dort feinmechanische Wunderwerke mit Dutzenden von Hebeln, Zahnrädern, Walzen und Federn besichtigen, wird enttäuscht. Erstens nämlich gibt es keine Besichtigungen - selbst die vier vor Ort arbeitenden Wissenschaftler und Techniker betreten die Seismometerkammer nur dann, wenn es unbedingt nötig ist, und das ist glücklicherweise selten. Zweitens würde der Besucher, selbst wenn er die Kammer betreten darf, nichts sehen als einige Styroporkisten und silbern glänzende Isolierfolien, die die Geräte vor den im Bergwerk ohnehin minimalen Temperaturschwankungen schützen. Drittens schließlich - nehmen wir an, ein Seismograph würde gerade neu aufgestellt und wäre daher unverhüllt zu sehen - stände dort auf einem kleinen Zementsockel lediglich ein geschlossener Metallzylinder, etwa so groß wie eine kleine Propangasflasche. In seinem Inneren, noch durch mehrfache weitere Abschirmungen geschützt, verbirgt sich der eigentliche Sensor: ein in einer Richtung frei beweglicher Messingklotz von einigen hundert Gramm Gewicht, die sogenannte seismische Masse. Ihre einzige Aufgabe ist es, ruhig zu bleiben, wenn um sie herum die Erde zittert. Ihre Lage wird elektronisch gemessen, auch hierfür braucht es keine Mechanik. Ganz ohne Feinmechanik kommt aber auch ein moderner Seismograph nicht aus: es ist gar nicht so einfach, eine Masse 'frei beweglich' im Schwerefeld der Erde aufzuhängen!Item Open Access Master-event correlation of weak local earthquakes by dynamic waveform matching(1993) Joswig, Manfred; Schulte-Theis, HartwigDynamic waveform matching (DWM) performs a non-linear correlation between two seismograms that are similar in shape but may be squeezed or stretched relative to each other. It extends the application of master-event comparisons to seismograms of greater spatial distance and retains the high-timing resolution of correlation techniques that act on the original time series. The DWM approach is applied to data recorded by a small array being part of the BOCHUM UNIVERSITY GERMANY (BUG) network which monitors the mining-induced seismicity in the Ruhr basin of NW Germany. The observed epicentres occur in clusters and therefore display only a limited number of seismogram waveform types. In one application an automatized cluster association with DWM obtains a resolution of about 100 metres at an epicentral distance of 200 to 40 km, using 10-20 defined master events for each region. These results are confirmed both by seismograms from a near-site station for mining-induced events from the Hamm region and by blast reports for a quarry region near Wuppertal. In another application of DWM, array traces from the BUG array are correlated to yield azimuth and slowness for epicentre location. as for the master event application, this approach is tuned for high performance on weak local events using a priori information about the approximate epicentral region. The implemented processes are shown to be capable of locating events with a rate of success equal to the performance of an experienced seismologist when processing all seismogrmas of four years BUG registration.Item Open Access Using GRACE data to study the impact of snow and rainfall on terrestrial water storage in Northeast China(2020) Qian, An; Yi, Shuang; Chang, Le; Sun, Guangtong; Liu, XiaoyangWater resources are important for agricultural, industrial, and urban development. In this paper, we analyzed the influence of rainfall and snowfall on variations in terrestrial water storage (TWS) in Northeast China from Gravity Recovery and Climate Experiment (GRACE) gravity satellite data, GlobSnow snow water equivalent product, and ERA5-land monthly total precipitation, snowfall, and snow depth data. This study revealed the main composition and variation characteristics of TWS in Northeast China. We found that GRACE provided an effective method for monitoring large areas of stable seasonal snow cover and variations in TWS in Northeast China at both seasonal and interannual scales. On the seasonal scale, although summer rainfall was 10 times greater than winter snowfall, the terrestrial water storage in Northeast China peaked in winter, and summer rainfall brought about only a sub-peak, 1 month later than the maximum rainfall. On the interannual scale, TWS in Northeast China was controlled by rainfall. The correlation analysis results revealed that the annual fluctuations of TWS and rainfall in Northeast China appear to be influenced by ENSO (EI Niño-Southern Oscillation) events with a lag of 2-3 years. In addition, this study proposed a reconstruction model for the interannual variation in TWS in Northeast China from 2003 to 2016 on the basis of the contemporary terrestrial water storage and rainfall data.Item Open Access Editorial for PFG issue 5/2023(2023) Gerke, Markus; Cramer, MichaelItem Open Access Knowledge-based seismogram processing by mental images(1994) Joswig, ManfredThe impact of pictorial knowledge representation is demonstrated for two examples of time series analysis in seismology. The approaches perform a) automated recognition of known event signatures and b) high-resolution onset timing of later phases. Both methods work well under extreme conditions of noise and achieved human-like performance in recognizing known situations. Crucial for this success of pictorial knowledge representation was the design of suitably scaled images. They must be simple and robust enough to transform the complexity of “real life” data into a limited set of patterns. These patterns differ significantly from the initial data; they correspond more closely to the non-linear weighting of recognized impressions by an experienced scientist. Thus the author addresses the pictorial presentations as mental images. For both reported applications, part of their power comes by model-based image modifications. However, this enhancement is far from demanding a complete theory. Any fractional model already enhances the image adaptation, so mental images are best suited to deal with incomplete knowledge like any other artificial intelligence approach. Cognitive plausibility was found for both the non-linear image scalings and the model-based image modifications. In general, the author's method of pictorial knowledge representation conforms to the concept of mental images by Kosslyn. Any new task will demand the composition of new, dedicated image transformations where some generalized design criteria are derived from the author's applications.