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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 35 (1987), S. 0 
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: We consider multiply covered traveltimes of first or later arrivals which are gathered along a refraction seismic profile. The two-dimensional distribution of these traveltimes above a coordinate frame generated by the shotpoint axis and the geophone axis or by the common midpoint axis and the offset axis is named a traveltime field.The application of the principle of reciprocity to the traveltime field implies that for each traveltime value with a negative offset there is a corresponding equal value with positive offset. In appendix A procedures are demonstrated which minimize the observational errors of traveltimes inherent in particular traveltime branches or complete common shotpoint sections.The application of the principle of parallelism to an area of the traveltime field associated with a particular refractor can be formulated as a partial differential equation corresponding to the type of the vibrating string. The solution of this equation signifies that the two-dimensional distribution of these traveltimes may be generated by the sum of two one-dimensional functions which depend on the shotpoint coordinate and the geophone coordinate. Physically, these two functions may be interpreted as the mean traveltime branches of the reverse and the normal shot. In appendix B procedures are described which compute these two functions from real traveltime observations by a least-squares fit.The application of these regressed traveltime field data to known time-to-depth conversion methods is straightforward and more accurate and flexible than the use of individual traveltime branches. The wavefront method, the plus-minus method, the generalized reciprocal method and a ray tracing method are considered in detail. A field example demonstrates the adjustment of regressed traveltime fields to observed traveltime data. A time-to-depth conversion is also demonstrated applying a ray tracing method.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-453X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Description / Table of Contents: Zusammenfassung In-situ-Spannungsmessungen im Kupferbergbau Mitterberg Im Kupferbergbau Mitterberg wurden in einer Seehöhe von 664 m und bei einer Überlagerung von 750 m In-situ-Spannungsmessungen mit Hilfe der Doorstopper-Methode durchgeführt. Es wurden dabei an zwölf Kernen innerhalb eines nach Osten orientierten Bohrloches Messungen durchgeführt. Mit Ausnahme der ersten drei Messungen behält die Achse der größten Dehnung ihre Richtung annähernd bei, so daß eine Mittelung sinnvoll erscheint. Zur Ermittlung desE-Moduls wurden Messungen mit der Goodman-Sonde vorgenommen. Diese Messungen erbrachten als weiteres Ergebnis auch Aufschlüsse über die Auflockerungszone um das Bohrloch. Die Ausdehnung der Auflockerungszone stand in Übereinstimmung mit der aus den Doorstopper-Messungen bestimmten größten Druckrichtung. Die Konvergenz der Verformungen einer benachbarten Strecke kann entweder durch die Ausbildung der Auflockerungszone entsprechend dem gemessenen Spannungsfeld oder durch die Anisotropie des geschieferten Gebirges erklärt werden.
    Abstract: Résumé Déterminations des contraintes en place dans la mine de cuivre à Mitterberg, Autriche Des déterminations des contraintes furent faites sur place dans la mine de cuivre à Mitterberg à une élevation de 664 m s. m., ce qui est 750 m en dessous de la surface. La méthode “doorstopper” fut utilisée; les déterminations furent faites avec 12 carottes prises dans un seul trou orienté vers l'Est. Si l'on élimine les 3 premières déterminations dans la zone près de la bouche du trou, les directions trouvées de la plus grande dilatation sont à peu près constantes; on peut alors former une moyenne. Le moduleE fut déterminé par une sonde de Goodman, ce qui permettait de calculer les contraintes. Comme resultat gratuit, les observations donnèrent aussi une indication de l'ampleur de la zone affaiblie autour du trou, dont la plus grande épaisseur fut trouvée dans la même direction que celle de la plus grande contrainte déterminée par la méthode “doorstopper”. La convergence des déformations d'une galerie dans le voisinage du point où les contraintes étaient determinées, peut être expliquée par la formation d'une zone affaiblie en correspondance avec le champ des contraintes déterminées ou par l'anisotropie causée par la foliation dans les roches.
    Notes: Summary In-Situ Stress Measurements in the Copper Mine at Mitterberg, Austria In-situ stress measurements were carried out in the copper mine at Mitterberg at a height of 664 m above sea level under a vertical overburden of 750 m. The “doorstopper”-method was applied. The measurements were made on 12 cores from one borehole which was directed towards the East. Except for the first three measurements which lay in a small depth range of the borehole behind a zone where retrieval of the cores was impossible, the scattering of the measurement values was rather small. Thus, a computation of mean values was significant. The determination of theE-modulus was carried out by means of a Goodman jack. These determinations gave additional information about the fracture zone around the borehole. The extent of the fracture zone was in agreement with the theoretical expectations regarding the direction of the maximum normal stress determined by the “doorstopper” measurements. The closure of an adjacent drive can be explained either by the development of a fracture zone in accordance with the stresses that were measured or because of an anisotropy in the foliated rock.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-453X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Description / Table of Contents: Zusammenfassung Die Rheologie des räumlich-kontinuierlichen Massenkriechens im Fels Aus der Literatur wurden Beschreibungen von räumlich kontinuierlichem Massenkriechen im Fels innerhalb der Ostalpen ausgewählt. Die Feldbeobachtungen wurden mit vier rheologischen Modellen (verallgemeinerte Newtonsche Flüssigkeit, Bingham-Körper, logarithmisches Kriechen, Kelvin-Körper) verglichen. Um auf das räumlich kontinuierliche Massenkriechen anwendbar zu sein, müssen die rheologischen Modelle folgende Bedingungen erfüllen: 1. Die Kriechgeschwindigkeit und der Spannungszustand zu Beginn der Kriechbewegung (Ende der letzten Eiszeit) sind aus der Extrapolation von gegenwärtigen Beobachtungen annähernd bekannt. 2. Der jetzige Spannungszustand und die gesamte Verschiebung seit Beginn der Kriechbewegung sind bekannt. 3. Die Deformation muß räumlich kontinuierlich sein und darf keine Blockbewegung ergeben. 4. Die Deformation kann sich nicht zur Gänze erholen. Nur das rheologische Modell des logarithmischen Kriechens entspricht allen Beobachtungsbefunden.
    Abstract: Résumé La rhéologie du fluage continu en espace des roches Des rapports sur le fluage continu des roches dans les Alpes orientales ont été choisis dans la littérature. L'information ainsi obtenu a été comparée avec quatre modèles rhéologiques (fluide de Newton généralisé, matériau de Bingham, fluage logarithmique, matériau de Kelvin) afin de vérifier leur applicabilité. Les conditions suivantes doivent être satisfaites par ces modèles rhéologiques: 1. La vitesse du fluage et les contraintes prévalentes au commencement du fluage (à la fin de la glaciation la plus récente) sont assez bien connues par une extrapolation des observations récentes. 2. Les contraintes dans le présent et le déplacement total depuis la dernière glaciation sont connus. 3. La déformation doit être continue dans l'espace et ne doit pas se faire “en bloc”. 4. La déformation ne peut pas être complètement reversible. Seul le modèle rhéologique du fluage logarithmique convient à toutes ces conditions.
    Notes: Summary The Rheology of Spacially Continuous Mass Creep in Rock Reports on spatially continuous mass creep in rock of the Eastern Alps have been selected from the literature. The information contained therein has been collated with four rheological models (generalized Newtonian fluid, Bingham body, logarithmic creep, Kelvin body) in order to test their applicability. The following conditions must be fulfilled by these rheological models: 1. The creep velocity and the state of stress prevailing at the beginning of the creeping motion (end of the last ice age) are fairly well known from the extrapolation of present day observations. 2. The state of stress at the present time and the total displacement since the beginning of the motion are known. 3. The deformation must be spatially continuous and not a block motion. 4. The deformation cannot be fully recoverable. Only the rheological model of logarithmic creep is appropriate to meet all these conditions.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2015-11-27
    Description: The increasingly dense coverage of Europe with broad-band seismic stations makes it possible to image its lithospheric structure in great detail, provided that structural information can be extracted effectively from the very large volumes of data. We develop an automated technique for the measurement of interstation phase velocities of (earthquake-excited) fundamental-mode surface waves in very broad period ranges. We then apply the technique to all available broad-band data from permanent and temporary networks across Europe. In a new implementation of the classical two-station method, Rayleigh and Love dispersion curves are determined by cross-correlation of seismograms from a pair of stations. An elaborate filtering and windowing scheme is employed to enhance the target signal and makes possible a significantly broader frequency band of the measurements, compared to previous implementations of the method. The selection of acceptable phase-velocity measurements for each event is performed in the frequency domain, based on a number of fine-tuned quality criteria including a smoothness requirement. Between 5 and 3000 single-event dispersion measurements are averaged per interstation path in order to obtain robust, broad-band dispersion curves with error estimates. In total, around 63,000 Rayleigh- and 27,500 Love-wave dispersion curves between 10 and 350 s have been determined, with standard deviations lower than 2 per cent and standard errors lower than 0.5 per cent. Comparisons of phase-velocity measurements using events at opposite backazimuths and the examination of the variance of the phase-velocity curves are parts of the quality control. With the automated procedure, large data sets can be consistently and repeatedly measured using varying selection parameters. Comparison of average interstation dispersion curves obtained with different degrees of smoothness shows that rough perturbations do not systematically bias the average dispersion measurement. They can, therefore, be treated as random but they do need to be removed in order to reduce random errors of the measurements. Using our large new data set, we construct phase-velocity maps for central and northern Europe. According to checkerboard tests, the lateral resolution in central Europe is ≤150 km. Comparison of regional surface-wave tomography with independent data on sediment thickness in North-German Basin and Polish Trough confirms the high-resolution potential of our phase-velocity measurements. At longer periods, the structure of the lithosphere and asthenosphere around the Trans-European Suture Zone (TESZ) is seen clearly. The region of the Tornquist-Teisseyre-Zone in the southeast is associated with a stronger lateral contrast in lithospheric thickness, across the TESZ compared to the region across the Sorgenfrei-Tornquist-Zone in the northwest.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 5
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 6
    Publication Date: 2019-07-16
    Description: The European Plate has a 4.5 Gy long and complex tectonic history. This is reflected in the present-day large-scale crustal structures. A new digital Moho depth map is compiled from more than 250 data sets of individual seismic profiles, 3-D models obtained by body and surface waves, receiver function results and maps of seismic and/or gravity data compilations. We have compiled the first digital, high-resolution map of the Moho depth for the whole European Plate, extending from the mid-Atlantic ridge in the west to the Ural Mountains in the east, and from the Mediterranean Sea in the south to the Barents Sea and Spitsbergen in the Arctic in the north. In general, three large domains within the European Plate crust are visible. The oldest Archean and Proterozoic crust has a thickness of 40–60 km, the continental Variscan and Alpine crust has a thickness of 20–40 km, and the youngest oceanic Atlantic crust has a thickness of 10–20 km.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 7
  • 8
    Publication Date: 2008-07-01
    Print ISSN: 0039-3169
    Electronic ISSN: 1573-1626
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Published by Springer
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  • 9
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    Seismological Society of America (SSA)
    Publication Date: 2018
    Description: 〈span〉〈div〉ABSTRACT〈/div〉Methods for location of seismic sources based on amplitudes provide an alternative to standard methods in cases with high ambient noise and emergent, multiple event, or tremor‐type source functions. Numerical methods using amplitudes or amplitude ratios have been described and successfully applied in several previous studies. In this article, a graphical location method based on amplitude ratios is presented, which may be of interest to students and others who want to learn about seismology due of its computational simplicity and the clarity of the solution.The most basic empirical relation to model the decay of the seismic amplitude maxima with distance is a power law. Given this relation, the ratio of the distances of two seismic stations to the seismic source is uniquely determined by the ratio of the amplitudes recorded at these stations. The geometrical loci of all points with a constant distance ratio is in what is known as an “Apollonius circle” in 2D, and in a sphere with the center and radius of the Apollonius circle in 3D. The graphical location method presented in this article considers the circular intersections of these spheres with a horizontal plane, preferentially in the level of the source location. Data from a low‐cost seismic sensor network in the southern Vienna basin are used to demonstrate the potential application of the method.〈/span〉
    Print ISSN: 0895-0695
    Electronic ISSN: 1938-2057
    Topics: Geosciences
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  • 10
    facet.materialart.
    Unknown
    Seismological Society of America (SSA)
    Publication Date: 2018
    Description: 〈span〉〈div〉ABSTRACT〈/div〉Methods for location of seismic sources based on amplitudes provide an alternative to standard methods in cases with high ambient noise and emergent, multiple event, or tremor‐type source functions. Numerical methods using amplitudes or amplitude ratios have been described and successfully applied in several previous studies. In this article, a graphical location method based on amplitude ratios is presented, which may be of interest to students and others who want to learn about seismology due of its computational simplicity and the clarity of the solution.The most basic empirical relation to model the decay of the seismic amplitude maxima with distance is a power law. Given this relation, the ratio of the distances of two seismic stations to the seismic source is uniquely determined by the ratio of the amplitudes recorded at these stations. The geometrical loci of all points with a constant distance ratio is in what is known as an “Apollonius circle” in 2D, and in a sphere with the center and radius of the Apollonius circle in 3D. The graphical location method presented in this article considers the circular intersections of these spheres with a horizontal plane, preferentially in the level of the source location. Data from a low‐cost seismic sensor network in the southern Vienna basin are used to demonstrate the potential application of the method.〈/span〉
    Print ISSN: 0895-0695
    Electronic ISSN: 1938-2057
    Topics: Geosciences
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