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  • Articles  (38)
  • 1985-1989  (16)
  • 1980-1984  (22)
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  • 1
    Electronic Resource
    Electronic Resource
    Synthetic body wave seismograms for laterally varying media containing thin transition layers (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 99 (1989), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: An approximate hybrid approach to computing high-frequency body wave synthetic seismograms in 2-D and 3-D laterally varying layered structures containing thin transition layers is suggested. It combines the ray method with the matrix (reflectivity) method. The ray method is applied to thick layers with smooth variations of velocity and the reflectivity method is applied to thin transition layers. Alternatively, the method of summation of Gaussian beams is used instead of the ray method in the hybrid code. An algorithm and the relevant program package BEAM87, designed for such hybrid computations in 2-D laterally varying layered structures containing one laterally varying thin transition layer, are briefly described. The thin transition layer may represent a region of a high velocity gradient, a laminated region, a region of a low Q, etc. It is simulated by a stack of very thin layers. The accuracy of the hybrid computations is tested on 1-D models by the comparison with reflectivity-method computations. The hybrid method yields sufficiently accurate results for transition layers, the thickness of which is smaller than one half of the prevailing wavelength of the wavefield under consideration, particularly for small angles of incidence. For reflected waves, the best accuracy is obtained for subcritical reflections, but the accuracy is lower for critical and overcritical reflections. The accuracy in the critical region is improved, if the Gaussian beam summation method is used instead of the ray method in the hybrid scheme. Numerical examples of synthetic body wave seismograms for a laterally varying model containing thin transition layers of various types are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1989.tb01692.x
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  • 2
    Electronic Resource
    Electronic Resource
    Ray tracing in factorized anisotropic inhomogeneous media (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 99 (1989), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A concept of a factorized anisotropic inhomogeneous (FAI) medium is introduced. In the FAI medium, the position dependent density normalized elastic parameters aijkl(Xi) can be factorized in the following sense: aijkl(Xi) =f2(xi)Aijkl, where Aijkl are constants, independent of Cartesian coordinates xi, and f(xi) is an arbitrary continuous function of xi. Thus, all the density normalized elastic parameters aijkl(xi) in the FAI medium depend on the coordinates xi in the same way, but the generality of anisotropy and of inhomogeneity is not restricted. The factorization of aijkl(xi) leads to a factorization of certain important ray theory expressions and equations (eikonal equation, etc.), and to particularly simple ray tracing and dynamic ray tracing. For certain types of FAI media, these equations may even be solved analytically or semianalytically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1989.tb02017.x
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  • 3
    Electronic Resource
    Electronic Resource
    ДИНАМИЧЕСКИЕ ПАРАМЕТРЫ СИЛЬНЫШ ЗЕМЛЕТРЯСЕНИЙ ПО ДАННЫМ ШИРОКОПОЛОСНОЙ ДЛИННОПЕРИОДНОЙ АППАРАТУРЫ (1980)
    Springer
    Studia geophysica et geodaetica 24 (1980), S. 142-152 
    Details
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Summary The dynamic focal parameters of a series of strong earthquakes, recorded by the FBV broadband velocigraph at KHC (Kašperské Hory, Czechoslovakia), are estimated. The influence of specific wave pattern features on the estimation accuracy is studied. Polarization analysis is used to demonstrate the complicated interference character even of record portions corresponding to a single teleseismic wave group. The values of the dynamic focal parameters do not depend significantly on the length of the analysed record portions and are sufficiently consistent with those reported by Riznichenko [2]. The possibility of estimating dynamic focal parameters from recording of standard classes B (intermediate band) and C (long-period) seismographs is pointed out.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01634408
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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    An analytical migration method for crustal wide angle reflections (1982)
    Springer
    Studia geophysica et geodaetica 26 (1982), S. 254-271 
    Details
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Summary An analytical migration method is developed for inverting wide angle seismic reflection travel time data with proper migration. In this method the concept of effective velocity (V eff ) in the vertically inhomogeneous earth has been used, which takes into account the refraction effect. It is shown that the migration process in this case becomes extremely rapid as curved ray paths are replaced by equivalent straight paths. A post migration ‘sliding correction’ is found to be necessary, which arises due to the non-collinearity of the recording point, reflection point and the image point in the equivalent straight path geometry for dipping reflectors. Calculations for some representative dips show that, for the depths and recording ranges of interest in DSS, the vertical component of the sliding correction is negligible compared to the horizontal component. However, even the horizontal component is not significant for reflectors with gentle dips. The effect of certain simplifying assumptions in the estimation of V eff is shown to be within the error limits of velocity determination. A computer programme package has been written for carrying out the migration. The method yields more accurate results in various theoretical and field cases than the conventional graphical wave front methods which are at present widely used for crustal reflection work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01635034
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Tensional crack development in physical models with inhomogeneities under load (1980)
    Springer
    Studia geophysica et geodaetica 24 (1980), S. 373-381 
    Details
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Summary The paper deals with a study of the mean stress field (σM) and its gradient (δσM/δx) in uniaxially loaded two-dimensional models of small thickness with respect to other dimensions, in which two inhomogeneities, e.g., a circular opening and a linear slit have been made. Particular attention was paid to the stress field development in the treated models durin gthe change of the mutual geometric configuration of both the inhomogeneities in question. The problem was analysed theoretically by means of Muskhelishvili's potentials of the two-dimensional theory of elasticity. To compare the results of calculations, the schlieren method was used to visualize and record the studied gradients of stress fields in physical models. The results of the calculations were calibrated by laboratory tests. In this way the individual model situations were classified from the point of view of their resistance to the applied load.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01629396
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  • 8
    Electronic Resource
    Electronic Resource
    Reduction of the number of knots in the approximation by smoothed cubic splines (1981)
    Springer
    Studia geophysica et geodaetica 25 (1981), S. 61-68 
    Details
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Summary A method of approximation, minimizing the number of knots and satisfying the smoothing and fitting properties of the cubic spline approximation, is suggested. Two modifications of the method are presented. The first approach is specified to provide an adequate simple approximation to the digitalized smooth curve (such as the velocity-depth function in seismology), while the second is more general and may be used to approximate geophysical measurements, which may include errors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01613561
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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    Reliability of focal mechanism determination (1981)
    Springer
    Studia geophysica et geodaetica 25 (1981), S. 224-230 
    Details
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Notes: Summary The fault plane solution determined by means of a computer algorithm, correlating the radiation pattern with the distribution of observations, was investigated from the point of view of its reliability. The maximum of the correlation function R corresponds to the optimum solution found by the computer. If the families of nodal lines fitting the decreased correlation function R —dR retain the character of the optimum solution even whendR increases, we assume that the solution has been determined with a sufficient accuracy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01591934
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