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  • 1
    Electronic Resource
    Electronic Resource
    The mechanism of small mining tremors from amplitude inversion (1989)
    Springer
    Pure and applied geophysics 129 (1989), S. 309-324 
    Details
    ISSN: 1420-9136
    Keywords: Inversion ofP- andS-wave amplitudes ; weak mining tremors ; shear-implosive source model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A method of inverting seismic wave amplitudes from mining tremors is proposed to reveal their mechanism. A simple shear-implosive model of a mechanism is proposed. The shapes of theoretical and observed radiation patterns are compared in the least squares norm and the parameters describing the shear-slip together with the ratio of implosive and shear dislocations are optimized. The efficiency of the method, even in the case of a small number of stations, is demonstrated by applying it to weak mining tremors from two mine regions in Czechoslovakia. The weak mining tremors are found to be of a predominantly shear mechanism with a clear coincidence of nodal planes to local tectonics, which could imply their tectonic nature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00874512
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  • 2
    Electronic Resource
    Electronic Resource
    Seismic events with non-shear component: II. Rock bursts with implosive source component (1985)
    Springer
    Pure and applied geophysics 123 (1985), S. 17-25 
    Details
    ISSN: 1420-9136
    Keywords: Rock burst mechanism ; Combination of shear and implosive displacements ; P-wave radiation patterns ; Field observations in coal mine regions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The rock burst mechanism of an implosive character is introduced and discussed; it is based on the idea that the compressional component of the stress field around the loaded stress concentrator can participate in the rock burst event. For easier classification of the rock burst from this viewpoint, a set of P-wave radiation patterns of the rock burst with a varying portion of the implosive component and varying propagation velocity of the displacements is presented and discussed. To support the credibility of the rock burst mechanism of an implosive character the seismic signals of the rock bursts from the mid-Bohemian coal district with negative signs of the P-wave first onsets are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877046
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  • 3
    Electronic Resource
    Electronic Resource
    Seismic events with non-shear component: I. Shallow earthquakes with a possible tensile source component (1985)
    Springer
    Pure and applied geophysics 123 (1985), S. 1-15 
    Details
    ISSN: 1420-9136
    Keywords: Physical modelling ; Tensile cracks ; Shallow earthquakes ; Radiation patterns ; Tensile seismic activity ; Combined shear-tensile seismic source
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The concept of seismicity of fast tensile fracturing is introduced and supported by the results of shear and of combined shear and tensile displacements along a loaded stress concentrator. The seismicity of tensile fracturing is demonstrated by means of acoustic (elastic) signals obtained during tensile fracturing in physical models under load; the basic physical relations between the parameters characterizing the loaded medium, load conditions, shear and tensile displacements, and release of acoustic energy are presented. For determining the tensile-source component in earthquakes a procedure based on the construction of radiation patterns is suggested and submitted for discussion. The criteria for selecting earthquakes with possible shear-tensile source mechanisms are listed and discussed. The existence of such a combined seismic source is sought in two shallow earthquakes which occurred in southern Iran in March 1977. In general, the paper should be regarded as a proposal to utilize the radiation characteristics of a seismic source—with all their insufficiencies—as a quick and simple tool for seeking combined shear and tensile mechanisms of seismic energy release.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877045
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  • 4
    Electronic Resource
    Electronic Resource
    Smoothing the source time function – a tool to soften inadequate modelling of the medium during inversion of local waveforms? (1998)
    Springer
    Journal of seismology 2 (1998), S. 145-158 
    Details
    ISSN: 1573-157X
    Keywords: smooth time function ; seismic source mechanism ; inexact structural model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The inconsistency of records of local earthquakes and synthetic seismograms due to noise contamination of the data and/or to improper Green function because of an inexact structural model often results in high frequency oscillations of the source time function, which prolongs it spuriously. A priori limit on the roughness of the source time function turned out to reduce the spurious oscillations but it keeps its spurious extension unchanged. Thus, it may yield a severe distortion of the seismic moment. However, it reduces the spurious volumetric component of the mechanism resulting from improper modelling of the structure and, thus, may help decide whether the retrieved volumetric component is real or false. The demand for the smoothness is incorporated as a penalty function in the minimization of the least square residuals, which allows us to decide about the degree of the smoothness. The minimization is performed with a simple genetic algorithm, which offers the advantage of a detailed exploration of the model space reducing the danger of being trapped in local minima.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008034914526
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  • 5
    Electronic Resource
    Electronic Resource
    Laboratory investigations on fault plane induced tensile cracks (1981)
    Springer
    Studia geophysica et geodaetica 25 (1981), S. 332-342 
    Details
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Summary Tensile cracks induced by stress concentration around a fault plane in physical models under uniaxial load were analyzed. The results characterizing the decisive role of the fault plane inclination to the the stress direction are presented. Two stages of tensile crack life were determined, i.e. the first, seismoactive stage, accompanied by seismic energy release and the second aseismic one characterized by low velocity of crack propagation. Results obtained seem to be relevant to a better understanding of the character and regime of actual seismoactive faults.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01629218
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  • 6
    Electronic Resource
    Electronic Resource
    Trajectory of fault-plane-induced tensile crack in relation to the primary stress field (1982)
    Springer
    Studia geophysica et geodaetica 26 (1982), S. 352-360 
    Details
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Summary The predetermination of the trajectory of a tensile crack induced at the tip of a stress-free fault plane (open slit, in two dimensional approximation) was investigated. Both the primary field of the tensile component of principal stress and the primary field of the strain energy density factor were computed and compared with the trajectory of the subsequent tensile crack. It was found that it is not the field of the strain energy density factor, but the field of the tensile component of principal stress which determines the trajectory of the tensile crack. Moreover, this field is responsible for the trajectory of the tensile crack not only in its seismoactive phase of its development, but also in the following aseismic stage characterized by slow stable growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01639636
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  • 7
    Electronic Resource
    Electronic Resource
    Propagation velocity and radiation properties of induced tensile cracks (1983)
    Springer
    Studia geophysica et geodaetica 27 (1983), S. 133-142 
    Details
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Резюме Изучены nлексuглaсные мо¶rt;елu квa¶rt;рamноŭ формы в коmорых вырезaнa ¶rt;uaгонaльнaя щель. Мо¶rt;елu нaгружaюmся о¶rt;ноосно ¶rt;о велuчuны крumuческoŭ нaгрузкu р uрu коmороŭ нa обоuх концaх щелu обрaзуюmся mрещuны оmрывa. Скоросmu рaсnросmрaненuя mрещuны оmрывa nре¶rt;ложены в зaвuсuмосmu оm углa нaклонa щелu к нanрaвленuю nрuложенноŭ нaгрузкu. Доnолнumельные ульmрaзвуковые uзмеренuя уnругuх uмnульсов uзученных во время nробега mрещuны оmрывa nре¶rt;осmaвuлu оnре¶rt;елumь временную фuнкцuю эmого uсmочнuкa. Полученные резульmamы ¶rt;uскуmuруюmся с mочкu зренuя мехaнuзмa хруnкого рaзрушенuя muna оmрывa кaк uсmочнuкa сеŭсмuческuх uмnульсов. По¶rt;робно aнaлuзuровaн учaсmок nробегa mрещuны оmрывa, в коmором uзлучaеmся сеŭсмuческaя энергuя.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01588986
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  • 8
    Electronic Resource
    Electronic Resource
    Source parameters for stick-slip and tensile-crack mechanisms and possibilities of their seismic discrimination (1983)
    Springer
    Studia geophysica et geodaetica 27 (1983), S. 143-156 
    Details
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Резюме Оmрывнaя mрещuнa uнuцuровaннaя рaзломом u сеŭсмоaкmuвныŭ с¶rt;вuг nо рaзлому былu uзучены в фuзuческuх мо¶rt;елях. Комбuнaцuеŭ мо¶rt;ельных эксnерuменmов u mеорuu былu оnре¶rt;елены очaговые naрaмеmры, сеŭсмuческuŭ моменm u сняmое нanряженuе ¶rt;ля мехaнuзмов оmрывноŭ mрещuны u сеŭсмоaкmuвного с¶rt;вuгa. Полученные резульmamы nокaзывaюm невыго¶rt;носmь эmuх очaговых naрaмеmров, обыкновенно оnре¶rt;еляемых нa сеŭсмологuческоŭ nрaкmuке, кaк крumерuŭ ¶rt;ля оmлuченuя рaссмamрuвaемых мехaнuзмов, u укaзывaюm неnрaвuльное оnре¶rt;еленuе эmuх naрaмеmров ¶rt;ля очaгов с комбuнuровaнным мехaнuзмом оmрывa u с¶rt;вuгa. Для рaссмamрuвaемых uсmочнuков былu вычuслены знaкu u aмnлumу¶rt;ы nервых всmуnленuŭ сеŭсмuческuх волн u былa nокaзaнa uх лучшaя nрuменumельносmь ¶rt;ля оmлuченuя с¶rt;вuговых u оmрывных мехaнuзмов нa основе сmaн¶rt;aрmноŭ сеŭсмологuческоŭ uнmерnреmaцuu.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01588987
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  • 9
    Electronic Resource
    Electronic Resource
    Comparison of Absolute and Relative Moment Tensor Solutions For The January 1997 West Bohemia Earthquake Swarm (2000)
    Springer
    Studia geophysica et geodaetica 44 (2000), S. 233-250 
    Details
    ISSN: 1573-1626
    Keywords: West Bohemia/Vogtland region ; earthquake swarm ; multiple event ; focal mechanisms ; moment tensor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Abstract Moment tensor solutions for 70 clustered events of the 1997 West Bohemia microearthquake swarm, as calculated by two different methods, are given. The first method is a single-event, absolute moment tensor inversion which inverts body-wave peak amplitudes using synthetic Green functions. The second method is a multiple-event, relative method for which Green functions are “reduced” to 2 geometrical angles of rays at the sources. Both methods yield similar moment tensors, which can be divided into at least two or three different classes of focal solutions, indicating that, during the swarm activity, different planes of weakness were active. The major source component of most events is a double couple. However, the deviations from the double-couple mechanisms seem to be systematic for some classes of solutions. Error analysis was based on transforming the estimate of the standard deviation of amplitudes extracting from the seismograms into confidence regions of the absolute moment tensor. They show that the non-DC components are significant at a fairly high confidence level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022166926987
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  • 10
    Electronic Resource
    Electronic Resource
    Anomalous behaviour of seismic waves at an interface between anisotropic media (1981)
    Springer
    Studia geophysica et geodaetica 25 (1981), S. 152-159 
    Details
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Summary An account of possible anomalous effects in reflection and refraction of elastic waves at an interface between anisotropic media is presented. These effects are due to anisotropy and they cannot occur at an interface between isotropic media. The shape of the slowness surface (its local deviations from spherical symmetry) is the decisive factor for appearance of these effects. A numerical example of such anomalous behaviour of elastic waves at a free boundary of the crystal of spinel is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01635370
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