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  • 1
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Description / Table of Contents: Summary The dependence between Pn-wave velocities and the surface heat flow, temperature at the core-mantl boundary and thickness of the Earth's crust for continents (Europe, Asia, North America and Australia) was investigated statistically in connection with the problem of lateral inhomogeneities in the upper mantle. The relations obtained were compared with those determined under laboratory conditions. The conclusion is that temperature and pressure effects may provide additional explanations of the regional variations of Pn-wave velocities observed in most continents.
    Notes: Резюме Зaвuсuмосmь меж¶rt;угрaнuчнымu скоросmямu nро¶rt;ольных волн нa nоверхносmu Мохоровuчuчa(Pn ), nоверхносmным mеnловым nоmоком, mемnерamуроŭ нa Мохо u мощносmью земноŭ коры конmuненmов былa uссле¶rt;овaнa в связu с воnросом о нрuчuнегорuзонmaльных нео¶rt;норо¶rt;носmеŭ скоросmu Pn. Оnублuковaнные ¶rt;aнные о резульmamaх лaборamорных uссле¶rt;овaнuŭ уnругuх своŭсmв nоро¶rt; верхнеŭ мaнmuu в условuях высокuх ¶rt;aвленuŭ u mемnерamур нaхо¶rt;umся в сооmвеmсmвuu с резульmamaмu nре¶rt;лaгaемоŭ рaбоmы. Делaеmся выво¶rt;, чmо регuонaльные uзмененuя скоросmеŭ Pn-волн ¶rt;ля больщеŭ чaсmu конmuненmaльноŭ коры оnре¶rt;еляюmся рaзлuчuем mермо¶rt;uнaмuческuх условuŭ нa nоверхносmu Мохоmовuчuчa.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    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.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    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.
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  • 4
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Description / Table of Contents: Summary A method of spectral analysis based on the prediction of the signal by means of AR parameters is proposed. The essence of this method ranks it between the classical methods of spectral analysis and the method of maximum entropy. For sufficiently high SNR its resolution is higher than that of the classical methods. The new method enables power and phase spectra of the signal to be determined, and provides a better determination of the power spectrum amplitude. than the method of maximum entropy. A regularization procedure is presented which abolished the instability of the prediction filter, obtained by the least-squares method.
    Notes: Резюме Пре¶rt;ложен сnособ сnекmрaльного aнaлuзa, основaнняыŭ нa nре¶rt;скaзaнuu сuгнaлa с nомощью aвmорегрессuонных naрaмеmров. Эmоm сnособ являеmся ¶rt;aльнеŭшuм рaзвumuем клaссuческuх мзmо¶rt;ов сnекmрaльного aнaлuзa с nрuвлеченuем u¶rt;еŭ uз меmо¶rt;a мaксuмaльноŭ энmроnuu. Сnособ облa¶rt;aеm nовышенноŭ рaэрешaющеŭ сnособносmью nо срaвненuю с клaссuческuмu меmо¶rt;aмu nрu aнaлuэе nроцессов с ¶rt;осmamочно хорошuм оmношенuем сuгнaл шум. Сnекmр мощносmu сuгнaлов оnре¶rt;еляеmср более нa¶rt;ежно, чем в меmо¶rt;е мaксuмaльноŭ энmроnuu. Воmлuчuе оm меmо¶rt;a мaксuмaльноŭ энmроnuu nре¶rt;ложенныŭ сnособ сnекmрaльного aнaлuзa nозволяеm оnре¶rt;еляmь mоже фaзовыŭ сnекmр сuгнaлов. Пaрaмеmры nре¶rt;скaзывaющего фuльmрa вычuсляюmся меmо¶rt;ом нauменьшuх квa¶rt;рamов, в коmором uсnользовaнa регулярuзaцuя ¶rt;ля вы¶rt;еленuя усmоŭчuвых облaсmеŭ решенuя.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Studia geophysica et geodaetica 30 (1986), S. 242-256 
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Description / Table of Contents: Summary The algorithm of iterative geophysical tomography is presented. The medium is approximated smoothly by means of B-splines. The tww-point problem of ray computation is solved with the aid of paraxial approximation. The parameters of the medium are obtained from the iterative algorithm of minimizing the quadratic form. Two numerical 2-D examples are given.
    Notes: Резюме Прuве¶rt;еи aлгорuфм umерamuвноŭгеофuзuческоŭ mомогрaфuu. Сре¶rt;a annроксuмuровaнa сnлощно nрu nомощu Б-сnлaŭнов. Пвухmочнaя nроблеммa рaсчемa лучеŭ рещенa nрu nомощu naрaксuaлноŭ annроксuмaцuu. Пaрaмеmры сре¶rt;ы nолучены иa основе umерamuвного aлгорuфмa мuнuмaлuзaцuu квa¶rt;рamuческоŭ формы. В рaбоmе nрuве¶rt;ены ¶rt;вa 2-D чuсленных nрuмерa.
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  • 6
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Description / Table of Contents: Summary The Gaussian beam method is applied to vertical seismic profiling in 2-D and 3-D models. A simple approach to the computation of Gaussian beam seismograms in the vicinity of structural interfaces is proposed. The effects of (a) the radiation pattern of a point source, (b) noncausal attenuation, (c) transverse inhomogeneities in synthetic seismograms are studied on numerical examples.
    Notes: Резюме Меmо¶rt; Гaуссевых nучков uсnользуеmся ¶rt;ля верmuкaльно о сеŭсмuческо о nрофuлuровaнuя в ¶rt;вух u mрехмерных мо¶rt;елях сре¶rt;ы. Уnоmребляеmся несложныŭ nо¶rt;хо¶rt; к рaсчеmу сеŭсмо рaмм в окресmносmu сmрукmурно о рaз¶rt;елa. Нa nрuмерaх сuнmеmuческuх сеŭсмо рaмм uзучaюmся эффекmы (a) uзлученuя mочечно о uсmочнuкa, (б) неnрuчнно о nо лощенuя u (в) nоnеречных нео¶rt;норо¶rt;носmеŭ.
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  • 7
    ISSN: 1573-1626
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
    Description / Table of Contents: Summary Localization errors made by approximating a given medium by a homogeneous rectangular block model and due to the approximative solution of two-point ray tracing are estimated for four different structures. The separate influence of the individual characteristics of the medium is discussed. The iterative Geiger method supplemented by a generalized inversion of the damped least-squares and Marquardt algorithm is used for localizating five hypothetical hypocentres using 9 stations. Travel times in the original structures, used as input data for localization, are calculated using a special ray tracing system.
    Notes: Резюме В рaбоmе оценены ошuбкu локaлuзaцuu вызвaнные annроксuмaцuеŭ реaльноŭ сре¶rt;ы мо¶rt;елеŭ сосmaвленноŭ uз орmогонaлных о¶rt;норо¶rt;ных блоков u annроксuмaцuеŭ mочного лучa ¶rt;вумя munaмu nрuблuзumельных лучеŭ.
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  • 8
    Publication Date: 1985-09-01
    Description: A method of spectral analysis based on the prediction of the signal by means of AR parameters is proposed. The essence of this method ranks it between the classical methods of spectral analysis and the method of maximum entropy. For sufficiently high SNR its resolution is higher than that of the classical methods. The new method enables power and phase spectra of the signal to be determined, and provides a better determination of the power spectrum amplitude. than the method of maximum entropy. A regularization procedure is presented which abolished the instability of the prediction filter, obtained by the least-squares method.РезюмеПре¶rt;ложен сnособ сnекmрaльно г о aнaлuзa, основaнняыŭ нa nре¶rt;скaзaнuu сu г нaлa с nомощью aвmоре г рессuонных naрaмеmров. Эmоm сnособ являеmся ¶rt;aльнеŭшuм рaзвumuем клaссuческuх мзmо¶rt;ов сnекmрaльно г о aнaлuзa с nрuвлеченuем u¶rt;еŭ uз меmо¶rt;a мaксuмaльноŭ энmроnuu. Сnособ облa¶rt;aеm nовышенноŭ рaэрешaющеŭ сnособносmью nо срaвненuю с клaссuческuмu меmо¶rt;aмu nрu aнaлuэе nроцессов с ¶rt;осmamочно хорошuм оmношенuем сu г нaл шум. Сnекmр мощносmu сu г нaлов оnре¶rt;еляеmср более нa¶rt;ежно, чем в меmо¶rt;е мaксuмaльноŭ энmроnuu. Воmлuчuе оm меmо¶rt;a мaксuмaльноŭ энmроnuu nре¶rt;ложенныŭ сnособ сnекmрaльно г о aнaлuзa nозволяеm оnре¶rt;еляmь mоже фaзовыŭ сnекmр сu г нaлов. Пaрaмеmры nре¶rt;скaзывaюще г о фuльmрa вычuсляюmся меmо¶rt;ом нauменьшuх квa¶rt;рamов, в коmором uсnользовaнa ре г улярuзaцuя ¶rt;ля вы¶rt;еленuя усmоŭчuвых облaсmеŭ решенuя. ©1985 ACADEMIA, Publishing House of the Czechoslovak Academy of Sciences
    Print ISSN: 0039-3169
    Electronic ISSN: 1573-1626
    Topics: Architecture, Civil Engineering, Surveying , Geosciences , Physics
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  • 9
    Publication Date: 1986-09-01
    Description: РезюмеПрuве¶rt;еи aл г орuфм umерamuвноŭ г еофuзuческоŭ mомо г рaфuu. Сре¶rt;a annроксuмuровaнa сnлощно nрu nомощu Б-сnлaŭнов. Пвухmочнaя nроблеммa рaсчемa лучеŭ рещенa nрu nомощu naрaксuaлноŭ annроксuмaцuu. Пaрaмеmры сре¶rt;ы nолучены иa основе umерamuвно г о aл г орuфмa мuнuмaлuзaцuu квa¶rt;рamuческоŭ формы. В рaбоmе nрuве¶rt;ены ¶rt;вa 2-D чuсленных nрuмерa.SummaryThe algorithm of iterative geophysical tomography is presented. The medium is approximated smoothly by means of B-splines. The tww-point problem of ray computation is solved with the aid of paraxial approximation. The parameters of the medium are obtained from the iterative algorithm of minimizing the quadratic form. Two numerical 2-D examples are given. ©1986 ACADEMIA, Publishing House of the Czechoslovak Academy of Sciences
    Print ISSN: 0039-3169
    Electronic ISSN: 1573-1626
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  • 10
    Publication Date: 1989-09-01
    Description: РезюмеМеmо¶rt; Гaуссевых nучков uсnользуеmся ¶rt;ля верmuкaльно о сеŭсмuческо о nрофuлuровaнuя в ¶rt;вух u mрехмерных мо¶rt;елях сре¶rt;ы. Уnоmребляеmся несложныŭ nо¶rt;хо¶rt; к рaсчеmу сеŭсмо рaмм в окресmносmu сmрукmурно о рaз¶rt;елa. Нa nрuмерaх сuнmеmuческuх сеŭсмо рaмм uзучaюmся эффекmы (a) uзлученuя mочечно о uсmочнuкa, (б) неnрuчнно о nо лощенuя u (в) nоnеречных нео¶rt;норо¶rt;носmеŭ.SummaryThe Gaussian beam method is applied to vertical seismic profiling in 2-D and 3-D models. A simple approach to the computation of Gaussian beam seismograms in the vicinity of structural interfaces is proposed. The effects of (a) the radiation pattern of a point source, (b) noncausal attenuation, (c) transverse inhomogeneities in synthetic seismograms are studied on numerical examples. ©1989 Academia, Publishing House of the Czechoslovak Academy of Sciences
    Print ISSN: 0039-3169
    Electronic ISSN: 1573-1626
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