In this research, we investigate the propagation of lateral electromagnetic wave near the surface of sea. Interference patterns generated by the superposition of the lateral and direct waves along the sea surface (fla...In this research, we investigate the propagation of lateral electromagnetic wave near the surface of sea. Interference patterns generated by the superposition of the lateral and direct waves along the sea surface (flat and rough) are shown. The field generated by a vertical magnetic dipole embedded below the sea surface (having a flat and perturbed upper surface) is shown to consist of a lateral-wave and a reflected-wave. Closed-form expressions for the lateral waves near the surface of the sea are obtained and compared with those mentioned for the reflected waves numerically for the con-sidered model.展开更多
This is an expand of the complex function method in solving the problem of interaction of plane.SH-waves and non-circular cavity surfaced with linig in anisotropic media.the use the method similar to that incorporated...This is an expand of the complex function method in solving the problem of interaction of plane.SH-waves and non-circular cavity surfaced with linig in anisotropic media.the use the method similar to that incorporated in [2] added with Savin's method for solving stress concentration of non-circular cavity surfaced with lining in elasticity.Anisotropic media can be used ic simulate the conditions of thegeology.The solving proceeding for this problem can be processed conveniently in the manner similar to that introduced in [2].In this paper.as illustrated in example numerical studies have been done for a square cavity surfaced with lining in anisotropic media.展开更多
For land seismic surveys, the surface waves are the dominant noises that mask the effective signals on seismograms.The conventional methods isolate surface waves from the effective signals by the differences in freque...For land seismic surveys, the surface waves are the dominant noises that mask the effective signals on seismograms.The conventional methods isolate surface waves from the effective signals by the differences in frequencies or apparent velocities,but may not perform well when these differences are not obvious. Since the original seismic interferometry can only predict inter-receiver surface waves, we propose the use of super-virtual interferometry(SVI), which is a totally data-driven method, to predict shot-to-receiver surface waves, since this method relieves the limitation that a real shot should collocate with one of the receivers for adaptive subtraction. We further develop the adaptive weighted SVI(AWSVI) to improve the prediction of dispersive surface waves, which may be generated from heterogeneous media at the near surface. Numerical examples demonstrate the effectiveness of AWSVI to predict dispersive surface waves and its applicability to the complex near surface. The application of AWSVI on the field data from a land survey in the east of China improves the suppression of the residual surface waves compared to the conventional methods.展开更多
new technique called the timefrequency polarization analysis was introduced in this paper. The technique combined the traditional surface wave analysis techniques (moving window and multifilter) with the singular valu...new technique called the timefrequency polarization analysis was introduced in this paper. The technique combined the traditional surface wave analysis techniques (moving window and multifilter) with the singular value decomposition method to measure the incidence azimuth of surface waves with different wavelengths. It was applied to study the propagation paths of surface waves across the different blocks of Chinese continent and different zones of QinghaiXizang (Tibet) plateau. The results show that the method can make full use of the differences in frequency compositions and arrival times of different surface wave modes, and give better polarization analysis results. The analysis by actual data shows that the lateral heterogeneity of the lithospheric structure influences the propagation paths of surface waves severely. Deviations of the paths across the QinghaiXizang plateau from great circle paths are great. Deviations of the surface waves across the different zones in QinghaiXizang plateau are different.展开更多
Study of seismic wave excitation and propagation in laterally heterogeneous media was an active and important subject in seismology in the past two decades, numerous analytical and numerical efforts have been made in ...Study of seismic wave excitation and propagation in laterally heterogeneous media was an active and important subject in seismology in the past two decades, numerous analytical and numerical efforts have been made in this research field. In this article, I have, first, made a brief review on those developments and then introduced and summarized a unified and efficient method, global generalized reflection-transmission (abbreviated to R/T thereafter) matrices method, for synthetic seismograms in multi-layered media with irregular interfaces developed by the author [24~26]. As demonstrated in this article, this method could be regarded as an extension of the generalized R/T coefficients method for the horizontally layered case [2,5] to the layered media with irregularly shaped interfaces by incorporating the T matrices technique [27,28]. Because of the use of a recursive scheme in computing the global generalized R/T matrices, this method is efficient, particularly for the case with a large number of展开更多
In this article, we have derived a new and more general formulation of Love waves in arbitrarily irregular multi-layered media by using the global generalized reflection/transmission (abbreviated to R/T thereafter) ma...In this article, we have derived a new and more general formulation of Love waves in arbitrarily irregular multi-layered media by using the global generalized reflection/transmission (abbreviated to R/T thereafter) matrices method developed earlier by Chen [17~20]. From the basic principle that the modal solutions are the non-trivial solutions of the free elastodynamic equation under appropriate boundary conditions, we naturally derived the characteristic frequencies and the corresponding distorted modes of Love wave in irregular multi-layered media. Moreover, we have derived the corresponding excitation formulation of Love waves in such laterally heterogeneous media by using the general solution of elastodynamic equation [17~20]. Similar to the result for laterally homogeneous layered structure, the Love waves radiated from a point source in irregular multi-layered media can be expressed as a superposition of distorted modes. Since the structure model used here is quite arbitrary, it can be used for展开更多
Two-dimensional scalar equation for the displacement of steady cross-plane shear (SH) waves in homogeneous and transversely isotropic media like unidirectional fibrous com-posites is given. Then, thrbugh a simple coor...Two-dimensional scalar equation for the displacement of steady cross-plane shear (SH) waves in homogeneous and transversely isotropic media like unidirectional fibrous com-posites is given. Then, thrbugh a simple coordinate system transform, the scalar equation is standardized into a Helmholtz equation. Corresponding integral equations are derived for the scattering problems and boundary element method (BEM) is used to calculate the scattered fields of arbitrarily shaped obstacles with both soft and rigid boudary conditions numerically.A discussion is given on the numerical results which is mainly focused on the influence of the a-nisotropy of the media to the directivity of the scattered fields by circular cylindrical voids.展开更多
文摘In this research, we investigate the propagation of lateral electromagnetic wave near the surface of sea. Interference patterns generated by the superposition of the lateral and direct waves along the sea surface (flat and rough) are shown. The field generated by a vertical magnetic dipole embedded below the sea surface (having a flat and perturbed upper surface) is shown to consist of a lateral-wave and a reflected-wave. Closed-form expressions for the lateral waves near the surface of the sea are obtained and compared with those mentioned for the reflected waves numerically for the con-sidered model.
文摘This is an expand of the complex function method in solving the problem of interaction of plane.SH-waves and non-circular cavity surfaced with linig in anisotropic media.the use the method similar to that incorporated in [2] added with Savin's method for solving stress concentration of non-circular cavity surfaced with lining in elasticity.Anisotropic media can be used ic simulate the conditions of thegeology.The solving proceeding for this problem can be processed conveniently in the manner similar to that introduced in [2].In this paper.as illustrated in example numerical studies have been done for a square cavity surfaced with lining in anisotropic media.
基金supported by the National Basic Research Program of China (Grant No. 2013CB228602)the National Science and Technology Major Project of China (Grant No. 2016ZX05004003-002)the National High Technology Research and Development Program of China (Grant No. 2013AA064202)
文摘For land seismic surveys, the surface waves are the dominant noises that mask the effective signals on seismograms.The conventional methods isolate surface waves from the effective signals by the differences in frequencies or apparent velocities,but may not perform well when these differences are not obvious. Since the original seismic interferometry can only predict inter-receiver surface waves, we propose the use of super-virtual interferometry(SVI), which is a totally data-driven method, to predict shot-to-receiver surface waves, since this method relieves the limitation that a real shot should collocate with one of the receivers for adaptive subtraction. We further develop the adaptive weighted SVI(AWSVI) to improve the prediction of dispersive surface waves, which may be generated from heterogeneous media at the near surface. Numerical examples demonstrate the effectiveness of AWSVI to predict dispersive surface waves and its applicability to the complex near surface. The application of AWSVI on the field data from a land survey in the east of China improves the suppression of the residual surface waves compared to the conventional methods.
文摘new technique called the timefrequency polarization analysis was introduced in this paper. The technique combined the traditional surface wave analysis techniques (moving window and multifilter) with the singular value decomposition method to measure the incidence azimuth of surface waves with different wavelengths. It was applied to study the propagation paths of surface waves across the different blocks of Chinese continent and different zones of QinghaiXizang (Tibet) plateau. The results show that the method can make full use of the differences in frequency compositions and arrival times of different surface wave modes, and give better polarization analysis results. The analysis by actual data shows that the lateral heterogeneity of the lithospheric structure influences the propagation paths of surface waves severely. Deviations of the paths across the QinghaiXizang plateau from great circle paths are great. Deviations of the surface waves across the different zones in QinghaiXizang plateau are different.
文摘Study of seismic wave excitation and propagation in laterally heterogeneous media was an active and important subject in seismology in the past two decades, numerous analytical and numerical efforts have been made in this research field. In this article, I have, first, made a brief review on those developments and then introduced and summarized a unified and efficient method, global generalized reflection-transmission (abbreviated to R/T thereafter) matrices method, for synthetic seismograms in multi-layered media with irregular interfaces developed by the author [24~26]. As demonstrated in this article, this method could be regarded as an extension of the generalized R/T coefficients method for the horizontally layered case [2,5] to the layered media with irregularly shaped interfaces by incorporating the T matrices technique [27,28]. Because of the use of a recursive scheme in computing the global generalized R/T matrices, this method is efficient, particularly for the case with a large number of
文摘In this article, we have derived a new and more general formulation of Love waves in arbitrarily irregular multi-layered media by using the global generalized reflection/transmission (abbreviated to R/T thereafter) matrices method developed earlier by Chen [17~20]. From the basic principle that the modal solutions are the non-trivial solutions of the free elastodynamic equation under appropriate boundary conditions, we naturally derived the characteristic frequencies and the corresponding distorted modes of Love wave in irregular multi-layered media. Moreover, we have derived the corresponding excitation formulation of Love waves in such laterally heterogeneous media by using the general solution of elastodynamic equation [17~20]. Similar to the result for laterally homogeneous layered structure, the Love waves radiated from a point source in irregular multi-layered media can be expressed as a superposition of distorted modes. Since the structure model used here is quite arbitrary, it can be used for
文摘Two-dimensional scalar equation for the displacement of steady cross-plane shear (SH) waves in homogeneous and transversely isotropic media like unidirectional fibrous com-posites is given. Then, thrbugh a simple coordinate system transform, the scalar equation is standardized into a Helmholtz equation. Corresponding integral equations are derived for the scattering problems and boundary element method (BEM) is used to calculate the scattered fields of arbitrarily shaped obstacles with both soft and rigid boudary conditions numerically.A discussion is given on the numerical results which is mainly focused on the influence of the a-nisotropy of the media to the directivity of the scattered fields by circular cylindrical voids.
