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Author: David E. Willis
Publisher:
ISBN:
Category : Seismic waves
Languages : en
Pages : 60
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Book Description
The report summarizes one year of theoretical and applied research on propagation of seismic waves and techniques for analyzing data. The main objectives were to determine the frequency and energy of seismic signatures, and investigate attenuation, patterns of azimuthal radiation from source regions, and methods of determining the type of motion at the source. Natural and artificial sources were studied to develop diagnostic aids for distinguishing between earthquakes and underground nuclear detonations. Equipment for selection, reformatting, and digital-to-analog conversion for digitally recorded LASA data was constructed and is being checked out. Several approaches for using the parallel computational capabilities of optics for LASA data were developed. A study of background noise and reciprocity for teleseismic events as recorded on the bottom of a large fresh water lake has commenced with the emplacement of three-component seismometers in Lake Superior. Array data have been used for crustal studies on the Eastern United States. Digital mode filtering was investigated. A perturbation theory for seismic sources was developed. (Author).
Author: David E. Willis
Publisher:
ISBN:
Category : Seismic waves
Languages : en
Pages : 60
Get Book Here
Book Description
The report summarizes one year of theoretical and applied research on propagation of seismic waves and techniques for analyzing data. The main objectives were to determine the frequency and energy of seismic signatures, and investigate attenuation, patterns of azimuthal radiation from source regions, and methods of determining the type of motion at the source. Natural and artificial sources were studied to develop diagnostic aids for distinguishing between earthquakes and underground nuclear detonations. Equipment for selection, reformatting, and digital-to-analog conversion for digitally recorded LASA data was constructed and is being checked out. Several approaches for using the parallel computational capabilities of optics for LASA data were developed. A study of background noise and reciprocity for teleseismic events as recorded on the bottom of a large fresh water lake has commenced with the emplacement of three-component seismometers in Lake Superior. Array data have been used for crustal studies on the Eastern United States. Digital mode filtering was investigated. A perturbation theory for seismic sources was developed. (Author).
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 92
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Book Description
The report discusses the results of an extensive long-range reversed refraction profile which traverses the Michigan Basin and the Appalachian Mountains. Particular emphasis is placed on the attenuation of first compressional wave arrivals and on crustal-upper mantle structure. Also included are results of a survey on lake bottom seismic background noise in Lake Superior. Although large signal levels were obtained in the lake bottom, long periods of high background noise indicated that land based seismographs are superior. Theoretical studies in elastic wave scattering were made to evaluate the effect of nonhomogeneities on the propagation of elastic waves. Theoretical development of mode filtering (previously demonstrated empirically), is nearly completed. A LASA digital data convertor was designed, constructed, and put into operation. Two- and three-dimensional seismic ray-tracing techniques using digital modeling were developed. These techniques enable the seismologist to determine the effects of lateral inhomogeneities and irregularities in velocity interfaces on travel time and attenuation of seismic waves. (Author).
Author: David E. Willis
Publisher:
ISBN:
Category : Seismic waves
Languages : en
Pages : 83
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Book Description
The report discusses the results of an extensive long-range reversed refraction profile which traverses the Michigan Basin and the Appalachian Mountains. Particular emphasis is placed on the attenuation of first compressional wave arrivals and on crustal-upper mantle structure. Also included are results of a survey on lake bottom seismic background noise in Lake Superior. Although large signal levels were obtained in the lake bottom, long periods of high background noise indicated that land based seismographs are superior. Theoretical studies in elastic wave scattering were made to evaluate the effect of nonhomogeneities on the propagation of elastic waves. Theoretical development of mode filtering (previously demonstrated empirically), is nearly completed. A LASA digital data convertor was designed, constructed, and put into operation. Two- and three-dimensional seismic ray-tracing techniques using digital modeling were developed. These techniques enable the seismologist to determine the effects of lateral inhomogeneities and irregularities in velocity interfaces on travel time and attenuation of seismic waves. (Author).
Author: Vernon L. Larrowe
Publisher:
ISBN:
Category : Fourier analysis
Languages : en
Pages : 215
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Book Description
Author: John F. HEMDAL
Publisher:
ISBN:
Category :
Languages : en
Pages : 25
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Book Description
Present day computer systems allow computation of an approximate Wiener operator for the time-domain filtering and smoothing of signals of finite and short length. However, the memory capacity of a particular computer storage introduces a constraint on the length of the operator and signal. To produce the least mean-square-error, it was helpful to know the extent to which the length of the operator should be compromised by including additional information(sample points) of the signal. If N is the number of samples of the signal to be equalized and T is the number of points in the optimum digital operator then the system imposes the constraint that KN + T(2)
Author: Johan O. A. Robertsson
Publisher: SEG Books
ISBN: 1560802901
Category : Nature
Languages : en
Pages : 115
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Book Description
The decades following SEG's 1990 volume on numerical modeling showed a step change in the application and use of full wave equation modeling methods enabled by the increase in computational power. Full waveform inversion, reverse time migration, and 3D elastic finite-difference synthetic data generation are examples. A searchable CD is included.
Author: Henry N. Pollack
Publisher:
ISBN:
Category :
Languages : en
Pages : 10
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Book Description
This paper studies the role of the cavity shape in determining the two-dimensional far-field radiation from a pressurized source. The radiation patterns are obtained for both the longitudinal and transverse waves radiating from an elliptical region that varies from a line source to a circular source. The results of several cases show that: (1) for all noncicular boundzries the shear wave exists and consistently shows a four-lobed pattern of alternate polarity. (2) the ratio of wavelength to cavity ecicumference and the cavity shape (ellipticity) have a strong influence on the radiation patter. (Author).
Author: Ivor K. McIvor
Publisher:
ISBN:
Category :
Languages : en
Pages : 23
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Book Description
Previous studies of the scattering of elastic waves have been limited to spherical and cylindrical scatterers. The present study is an investigation of the scattering of a plane compressional wave incident from an arbitrary direction on an elliptical obstacle (either cavity or a rigid inclusion). By varying the ellipticity, shapes ranging from the finite-length slit to the cylinder may be considered. Analytical solutions are obtained for the scattered displacements in the form of product series expansions valid throughout the entire media. Due to the interaction of P-waves and S-waves at the boundary of the scatterer, the boundary conditions are not separable. As a consequence the coefficients of the series solution are determined from a coupled, infinite system of algebraic equations. The solutions are highly convergent, however, and the system can be truncated to a reasonable size for numerical computation. In addition, simplified asymptotic solutions are given for the far-field displacements. It is found that the scattered displacements attenuate like r to the minus one-half power, with the radial displacement associated with the dilatational potential and the tangential displacement associated with the shear potential. The asymptotic solutions are used to obtain the scattered radiation pattern in the far field. Finally, for the special case of a slit the radiation patterns for different directions of incident wave and different ratios of wave length to slit length are compared. (Author).
Author: Masaki Kanao
Publisher: BoD – Books on Demand
ISBN: 9533079444
Category : Science
Languages : en
Pages : 340
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Book Description
The importance of seismic wave research lies not only in our ability to understand and predict earthquakes and tsunamis, it also reveals information on the Earth's composition and features in much the same way as it led to the discovery of Mohorovicic's discontinuity. As our theoretical understanding of the physics behind seismic waves has grown, physical and numerical modeling have greatly advanced and now augment applied seismology for better prediction and engineering practices. This has led to some novel applications such as using artificially-induced shocks for exploration of the Earth's subsurface and seismic stimulation for increasing the productivity of oil wells. This book demonstrates the latest techniques and advances in seismic wave analysis from theoretical approach, data acquisition and interpretation, to analyses and numerical simulations, as well as research applications. A review process was conducted in cooperation with sincere support by Drs. Hiroshi Takenaka, Yoshio Murai, Jun Matsushima, and Genti Toyokuni.
