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  • 1
    Electronic Resource
    Electronic Resource
    Seismic regime of a single fault model (1986)
    Springer
    Pure and applied geophysics 124 (1986), S. 793-810 
    Details
    ISSN: 1420-9136
    Keywords: Plate models ; shear and tensile source mechanisms ; seismotectonic interpretation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879611
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  • 2
    Electronic Resource
    Electronic Resource
    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
    Keywords: Fault interaction ; seismotectonic interpretation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00879615
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  • 3
    Electronic Resource
    Electronic Resource
    A combined study of macroseismic data and focal mechanisms applied to the West-Bohemian earthquake, Czechoslovakia (1990)
    Springer
    Pure and applied geophysics 133 (1990), S. 53-71 
    Details
    ISSN: 1420-9136
    Keywords: Macroseismic data ; synthetic isoseismals ; focal mechanism ; earthquake swarm ; circular-source model ; local geological conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The main shock of the West-Bohemian earthquake swarm, Czechoslovakia, (magnitudem=4.5, depthh=10 km) exhibits an irregular areal distribution of macroseismic intensities 6° to 7° MSK-64. Four lobes of the 6° isoseismal are found and the maximum observed intensity is located at a distance of 8 km from the instrumentally determined epicentre. This distribution can be explained by the energy flux of the directS wave generated by a circular source, the hypocentral location and focal mechanism of which are taken from independent instrumental studies. The theoretical intensity, which is assumed to be logarithmically proportional to the integrated squared ground-motion velocity (i.e.,I=const+log ∫v 2 (t)dt), fits the observed intensity with an overall root-mean-square error less than 0.5°. It is important that the present intensity data can also be equally well explained by the isotropic source. The fit was attained by means of a horizontally layered model though large fault zones and an extended sedimentary basin suggest a significant lateral heterogeneity of the epicentral region. The results encourage a broader application of the simple modelling technique used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876702
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  • 4
    Electronic Resource
    Electronic Resource
    Elastic Parameters of West Bohemian Granites under Hydrostatic Pressure (1998)
    Springer
    Pure and applied geophysics 151 (1998), S. 631-646 
    Details
    ISSN: 1420-9136
    Keywords: Key words: Granite, Bohemian Massif, P-wave velocity, velocity anisotropy, fabric elements, hydrostatic pressure.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000240050134
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  • 5
    Electronic Resource
    Electronic Resource
    Seismically active fracture zones and distribution of large accumulations of metals in the central part of Andean South America (2000)
    Springer
    Mineralium deposita 35 (2000), S. 2-20 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The analysis of the geometry of distribution of earthquake foci in the central part of Andean South America between 18° and 34°S made the delineation of several seismically active fracture zones in the continental wedge overlying the subducting Nazca plate possible. Correlation of their position with the distribution of hypogene accumulations of metals revealed that the majority of large mineral deposits and mining districts are situated in the outcrops of these fracture zones. We present geometrical documentation (map of epicentres, vertical and longitudinal cross sections) of the most important fracture zones and data on mineralogical composition, genetic type and available radiometric ages of mineral deposits. Sixteen mining districts in Chile, and 24 in Argentina, were attributed to the seismically active fracture zones. Major mining districts and individual large mineral deposits occur in six seismically active fracture zones roughly parallel to the axis of the Peru-Chile trench (Carachas-Portillo, Choquelimpie, Iquique, Domeyko, Río Blanco-Los Bayos and Farellones F.Z.), in six fracture zones roughly perpendicular to the trench (El Salvador, Maricunga, Jaroma, Ujina, Tumbaya and Incahuasi-León Muerto F.Z.) and in two fracture zones oriented at an angle of about 45° in relation to the direction of the presently active Andean subduction (Aconcagua and Sierra del Volcán F.Z.). The occurrences of large mineral deposits of different ages show that these fracture zones were also active in the geological past and represent sites of permanent re-opening of paths allowing ore-bearing solutions and long-term accumulation of large amounts of metals to occur in relatively restricted domains of the Earth's crust. The mining districts with dated mineral deposits are arranged into four periods of hypogene mineralization: Upper Miocene-Pliocene, Upper Oligocene-Middle Miocene, Upper Eocene-Middle Oligocene, Lower Paleocene-Upper Eocene. These periods of metallogenic activity correlate well with four supposed Andean subduction cycles active in the Tertiary. The occurrence of mineral deposits of different ages in recently active fracture zones can be used as an important evidence in favour of long-term spatial permanence and activity of these zones and as a guide for the discovery of further mineral deposits hidden under young sedimentary and volcanic cover in the fracture zones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00002968
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  • 6
    Electronic Resource
    Electronic Resource
    Interpretation of tectonic stress orientation on the basis of laboratory model experiments
    Amsterdam : Elsevier
    Physics of the Earth and Planetary Interiors 51 (1988), S. 101-106 
    Details
    ISSN: 0031-9201
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0031-9201(88)90028-3
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  • 7
    Electronic Resource
    Electronic Resource
    Wave propagation in physical models of micromorphic media (1984)
    Springer
    Studia geophysica et geodaetica 28 (1984), S. 272-285 
    Details
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Description / Table of Contents: Summary The propagation of seismic waves in a micromorphic body, which is supposed to be one of the possible models of the medium in the earthquake focus, is studied by means of the two-dimensional ultrasonic model technique. The results obtained indicate that such a medium is characterized by distinct elastic anisotropy and by increased attenuation. The propagation velocity of longitudinal waves decreases and their amplitudes change considerably. The prevailing frequency of the waves passing through the micromorphic medium tends smoothly to one value which depends on the space distribution, orientation and dimensions of the elements characterizing such a medium. The obtained results are confronted with the theory of a micromorphic medium.
    Notes: Резюме Рaсnросmрaненuе сеŭсмuческuх волн в мuкроморфноŭ сре¶rt;е, nо mеорuu о¶rt;ноŭ uз возможных мо¶rt;елеŭ сре¶rt;ы в очaге землеmрясенuя, uзучaеmся nуmём ¶rt;вухмерного ульmрaзвукового мо¶rt;елuровaнuя. Полученные резульmamы nокaзывaюm, чmо maкaя сре¶rt;a оmлuчеamся яркоŭ уnругоŭ aнuзоmроnuеŭ u nовыщенным nоглощенuе⇐. Скоросmь рaсnросmрaненuя nрохо¶rt;ящuх nро¶rt;ольных волн nонuжaеmся, uх aмnлumу¶rt;ы резко меняюmся. Преовлa¶rt;aющaя чaсmоma волн, nрохо¶rt;ящuх мuкроморфноŭ сре¶rt;оŭ, nлaвно сmремumся к о¶rt;ноŭ велuчuне, коmорaя связaнa с nросmрaнсmвенным рaсnре¶rt;еленuем, нanрaвленносmью u рaзмерaмu ¶rt;ефекmов, оnре¶rt;еляющuх эmу сре¶rt;у. Полученые резульmamы срaвнuвaюmся с mеорuеŭ мuкроморфноŭ сре¶rt;ы.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01589608
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  • 8
    Electronic Resource
    Electronic Resource
    Repeated Geodetic Measurements in the West Bohemia Seismoactive Region: Period 1993 - 1996 (1997)
    Springer
    Studia geophysica et geodaetica 41 (1997), S. 319-328 
    Details
    ISSN: 1573-1626
    Keywords: earthquake swarms ; surface deformations ; GPS ; precise levelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Abstract The western part of the Bohemian Massif is characterized by repeated occurrences of intraplate earthquake swarms. To study surface deformations of this anomalous region, a network covering about 2000 square kilometres for repeated geodetic measurements was established in 1993 - 1994. The positions of the individual points of the network were carefully picked with respect to local tectonic structure and earthquake foci distribution. GPS and precise levelling measurements were performed 1-2 times a year. The GPS data were processed by Bernese GPS software. No tendency to any displacement - either horizontal or vertical - of geological blocks was derived from the geodetic data for the period 1993 - 96. Only displacements of less than 5 mm/year in average could occur in the whole region in that period; larger displacements would have been revealed by our measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023355300199
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  • 9
    Electronic Resource
    Electronic Resource
    Earthquake Swarms and Accompanying Phenomena in Intraplate Regions: A Review (2000)
    Springer
    Studia geophysica et geodaetica 44 (2000), S. 89-106 
    Details
    ISSN: 1573-1626
    Keywords: earthquake swarms ; Quaternary volcanism ; fluids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Abstract The western part of the Bohemian Massif has played an exceptional role in recent geodynamic activity of the region. It is characterised by repeated occurrences of earthquake swarms and by other manifestations of deep tectonic processes (CO 2 emissions, anomalous 3 He content, mineral waters, mofettes, etc.). The purpose of this paper is to introduce some other intraplate regions with earthquake swarm occurrence (French Massif Central; Colli Albani and Vulsini Mts., central Italy; Southern Apennines, Italy; the Danville and Long Valley regions, California; central Arkansas), and with artificially induced earthquake swarms (Larderello, Italy, geothermal field; Coso, California, geothermal field; NE Bavaria, Germany, deep drilling project). Although these areas represent different tectonic environments, the manifestations of recent geodynamic and/or man-made activity are similar in many aspects. This coincidence most probably issues from a common cause of both tectonic and artificially induced earthquake swarms – intrusions/injections of fluids. Since the regions with earthquake swarm occurrence of tectonic origin are situated as a rule in the close neighbourhood of Quaternary volcanoes, the intruding fluids seem to be derived from magma recently transported to upper crustal layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022146422444
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  • 10
    Electronic Resource
    Electronic Resource
    Migration of Events During The January 1997 Earthquake Swarm (The West Bohemia/Vogtland Region) (2000)
    Springer
    Studia geophysica et geodaetica 44 (2000), S. 227-232 
    Details
    ISSN: 1573-1626
    Keywords: West Bohemia/Vogtland region ; earthquake swarms ; migration ; fluids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Abstract A detailed analysis of the time-space pattern of seismic activity during the January 1997 swarm demonstrates the gradual and ordered migration of earthquake foci, suggesting a step-by-step penetration of crustal fluids into a remarkably small fractured volume.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022114910149
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