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  • 1
    Digitale Medien
    Digitale Medien
    Influence of Nonlinear Processes in Seismic Foci on Released Energy (1997)
    Springer
    Pure and applied geophysics 149 (1997), S. 337-355 
    Details
    ISSN: 1420-9136
    Schlagwort(e): Key words: Self-synchronisation, nonlinear effects, seismic energy release, rock bursts, amplitude- phase analysis, relative width of frequency spectra.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract —The results of the frequency analysis of seismoacoustic elastic waves radiated from the loaded rock sample source models and of rock bursts records are presented. For both categories of study the fundamental symptoms of nonlinear processes in seismic foci were found and demonstrated. Namely, the wave-field modulation (satellites in the spectra), forced synchronisation (spectra simplification and their transformation into a narrow spectral band), frequency shift to lower values and, finally, coherency of radiation. A new method of amplitude-phase distribution is worked out. All this indicates that nonlinear processes can participate in a seismic source during the energy release. Also, the disagreement between the source sizes observed in the nature and computed by means of linear physics, can be explained by self-organising processes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s000240050029
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  • 2
    Digitale Medien
    Digitale Medien
    Laboratory Approach to the Study of Elastic Anisotropy on Rock Samples (1998)
    Springer
    Pure and applied geophysics 151 (1998), S. 619-629 
    Details
    ISSN: 1420-9136
    Schlagwort(e): Key words: Laboratory measurements, elastic anisotropy, kinematic and dynamic parameters of elastic waves, hydrostatic pressure.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract —The experimental approach (hardware and software) to the study of the elastic an isotropy of rocks on spherical samples under hydrostatic pressure up to 400 MPa is discussed. A substantial innovation of the existing measuring system and processing methods enabled us to make a detailed investigation and evaluation of the kinematic as well as dynamic parameters of elastic waves propagating through anisotropic media. The innovation is based on digital recording of the wave pattern with a high sampling density of both time and amplitude. Several options and results obtained with the innovated laboratory equipment are presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s000240050133
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  • 3
    Digitale Medien
    Digitale Medien
    Elastic Parameters of West Bohemian Granites under Hydrostatic Pressure (1998)
    Springer
    Pure and applied geophysics 151 (1998), S. 631-646 
    Details
    ISSN: 1420-9136
    Schlagwort(e): Key words: Granite, Bohemian Massif, P-wave velocity, velocity anisotropy, fabric elements, hydrostatic pressure.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract —The West Bohemian seismoactive region is situated near the contact of the Moldanu bian, Bohemian and Saxothuringian units in which a large volume is occupied by granitoid massifs. The spatial distribution of P-wave velocities and the rock fabric of five representative samples from these massifs were studied. The P-wave velocities were measured on spherical samples in 132 independent directions under hydrostatic pressure up to 400 MPa, using the pulse-transmission method. The pressure of 400 MPa corresponds to a depth of about 15 km in the area under study. The changes of P-wave velocity were correlated with the preferred orientations of the main rock fabric elements, i.e., rock forming minerals and microcracks. The values of the P-wave velocity from laboratory measurements on granite samples fit the velocity model used by seismologists in the West Bohemian seismoactive region.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s000240050134
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  • 4
    Digitale Medien
    Digitale Medien
    Seismic regime of a single fault model (1986)
    Springer
    Pure and applied geophysics 124 (1986), S. 793-810 
    Details
    ISSN: 1420-9136
    Schlagwort(e): Plate models ; shear and tensile source mechanisms ; seismotectonic interpretation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract A special experimental technique enabled us to study in detail seismic events on a fault model in a uniaxial stress field. The recording system used made it possible to investigate the radiation pattern for all the events observed including the precise determination of the dislocation origin. The aim of the present paper is (1) to find the relation between shear and tensile displacements, (2) to check a possible influence of the process of tensile crack generation on the seismic energy release and (3) to compare the seismic regime of a single fault before and after the tensile crack generation, respectively. Results prove the dominating importance of shear mechanism for the seismic energy release. The tensile displacement can be seismoactive only under special contact conditions on the fault plane. The existence of tensile cracks at the fault tips changed the pattern of seismic energy radiation. This feature is probably caused by subsequent changes in contact conditions on the fault plane and in the stress field around the fault. A comparison of some results of the present model experiments with the already published results of geological and seismological measurements and investigations shows the analogous character in laboratory and in nature of the process of tectonic earthquake preparation, the displacement course on the fault during the earthquake and the manner of seismic energy release on faults.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00879611
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  • 5
    Digitale Medien
    Digitale Medien
    Fault interaction and seismicity: Laboratory investigation and its seismotectonic interpretation (1986)
    Springer
    Pure and applied geophysics 124 (1986), S. 857-874 
    Details
    ISSN: 1420-9136
    Schlagwort(e): Fault interaction ; seismotectonic interpretation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Systems of two parallel linear faults of the same length with the angle of inclination α=45° were investigated under uniaxial linearly increasing load. Perspex plates were used as models. For each treated fault configuration the morphology of tensile cracks and the sequence of seismoacoustic events of shear and tensile origin were studied. It is shown that the seismic regime of a fault system is strongly influenced by the contact conditions on a fault plane; it is different in the faults with the aseismic contact, represented by open slits, and in the faults with the seismoactive contact, represented by filled slits, respectively. The experiments proved the dominating role of a fast shear displacement of the stick-slip type in the regime of seismic energy release of a fault system. The tensile crack generation seems to be only of little—if not negligible—importance. On the other hand, the existence of tensile cracks in a fault system can play an important role in the course of subsequent loading cycles because the stick-slip displacements can take place not only along the primary faults but also along the planes of tensile cracks. A comparison of some results of model experiments and the already published results of geological and seismological investigations indicated that the way of seismic energy relase on faults in nature and in the laboratory could be of the same character. Several analogies between the seismic regime of a fault model and of real seismic regions were found concerning the morphology of faults, off-fault fore- and aftershocks, and earthquake doublets, respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00879615
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  • 6
    Digitale Medien
    Digitale Medien
    Nonlinear processes in earthquake foci (1993)
    Springer
    Pure and applied geophysics 140 (1993), S. 29-47 
    Details
    ISSN: 1420-9136
    Schlagwort(e): Rock samples ; biaxial compression ; seismogenic structures ; nonlinear processes ; wave coherency ; selforganizing ; underload
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The results of laboratory experiments on biaxially compressed physical models of a seismic source are presented, discussed and interpreted in terms of nonlinear dynamics; the relation is shown between the degree of seismic pulse coherency (expressed through the amplitude frequency spectra development) and energy (or magnitude) in a series of model experiments. It has been ascertained that the degree of radiated waves coherency plays a more important role concerning the seismic energy release than the size (radius) of the seismic source. The relations among individual source parameters obtained in the laboratory were tested by the analysis of three series of seismograms of aftershocks which followed the 1988 Spitak earthquake (two series) and the 1975 Oroville earthquake (one series). The fundamental effect observed in the laboratory, i.e., the growth of pulse coherency with increasing stress concentration in the focal region (reflected in growing earthquake magnitude), was clearly manifested in all three earthquake aftershock series. Due to derivation by a comparison of the above results, obtained on the basis of nonlinear dynamics with the classical source models by Brune, Madariaga and others, it seems to be namely the self-organizing of the structure itself caused by the increasing stress field in the seismic source, which can answer the question concerning the degree of energy cumulation in the earthquake focus at a given moment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00876869
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  • 7
    Digitale Medien
    Digitale Medien
    Stick-slip unstable shear failure as a source of high frequency elastic radiation (1989)
    Springer
    Studia geophysica et geodaetica 33 (1989), S. 322-337 
    Details
    ISSN: 1573-1626
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie , Physik
    Notizen: Summary The results of laboratory measurements on square perspex models with a stress concentrator under uniaxial compression are presented. An attempt was made to interpret these results in order to determine the mutual relations between the mechanical parameters characterizing the treated models, including their focal zones, parameters of model loading, parameters of seismogenic displacement and parameters of radiated elastic pulses. Particular attention was given to the study of slip displacement, slip velocity, rupture velocity, nucleation points of rupture propagation, nucleation points of elastic radiation and to the frequency analysis of radiated pulses. Measurements of the displacement in the focal zone enabled us to determine the source function, to construct theoretical seismograms in a far field and to compare them with the real pulses from ultrasonic transducers located there. This allowed testing theoretical and experimental approaches to the study of how slip displacement, slip velocity and rupture velocity are related to the parameters of radiated pulses.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01637688
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  • 8
    facet.materialart.
    Unbekannt
    Bulk rock elastic moduli at high pressures, derived from the mineral textures and from extrapolated laboratory data (2015)
    IOP Publishing
    In:  IOP Conference Series: Materials Science and Engineering, 82 (1). 012093.
    Details
    Publikationsdatum: 2019-01-15
    Beschreibung: The elastic anisotropy of bulk rock depends on the mineral textures, the crack fabric and external parameters like, e.g., confining pressure. The texture-related contribution to elastic anisotropy can be predicted from the mineral textures, the largely sample-dependent contribution of the other parameters must be determined experimentally. Laboratory measurements of the elastic wave velocities are mostly limited to pressures of the intermediate crust. We describe a method, how the elastic wave velocity trends and, by this means, the elastic constants can be extrapolated to the pressure conditions of the lower crust. The extrapolated elastic constants are compared to the texture-derived ones. Pronounced elastic anisotropy is evident for phyllosilicate minerals, hence, the approach is demonstrated for two phyllosilicate-rich gneisses with approximately identical volume fractions of the phyllosilicates but different texture types.
    Materialart: Article , PeerReviewed
    Format: text
    DOI: 10.1088/1757-899X/82/1/012093
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    OceanRep: Artikel in einer Fachzeitschrift - begutachtet
  • 9
    facet.materialart.
    Unbekannt
    Performance of almost edgeless silicon detectors in CTS and 3D-planar technologies (2013)
    Institute of Physics Publishing (IOP)
    Details
    Publikationsdatum: 2013-06-15
    Beschreibung: The physics programme of the TOTEM experiment requires the detection of very forward protons scattered by only a few microradians out of the LHC beams. For this purpose, stacks of planar Silicon detectors have been mounted in moveable near-beam telescopes (Roman Pots) located along the beamline on both sides of the interaction point. In order to maximise the proton acceptance close to the beams, the dead space at the detector edge had to be minimised. During the detector prototyping phase, different sensor technologies and designs have been explored. A reduction of the dead space to less than 50 μm has been accomplished with two novel silicon detector technologies: one with the Current Terminating Structure (CTS) design and one based on the 3D edge manufacturing. This paper describes performance studies on prototypes of these detectors, carried out in 2004 in a fixed-target muon beam at CERN's SPS accelerator. In particular, the efficiency and accuracy in the vicinity of the beam-f...
    Digitale ISSN: 1748-0221
    Thema: Physik
    Publiziert von Institute of Physics Publishing (IOP)
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    PAPER CURRENT
  • 10
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    Unbekannt
    Acoustic Emission event onsets recognized by Neural Network formalism (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publikationsdatum: 2023-05-02
    Beschreibung: One of the contemporary trend in seismology is process huge data sets automatically with use of Neural Network (NN) formalism. We present seismogram onsets interpretation obtained both by Convolution NN as well as Recurrent NN approach. We investigated data from Acoustic Emission loading experiment with Westerly Granite. Such data appeared to be suitable for testing of NN approach as they are more homogeneous then data originated from natural earthquakes, but simultaneously they are complex enough not to be of trivial interpretation. We designed NN architecture, learned in and compare the results with biased interpretation. We were searching not only for onsets on individual seismograms but we try to identified the whole events. In addition to automatic onsets identification we (also automatically) determined event location and seismic moment tensor. Comparison with biased data proved that these automatically obtained values can be successfully used as preliminary estimation at least. Problems of multiple events identification are discussed as well. The method has a potential to be applicable on natural earthquake seismograms.
    Sprache: Englisch
    Materialart: info:eu-repo/semantics/conferenceObject
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