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Exact synthetic seismograms for an inhomogeneity in a layered elastic half-space

Karlsson, Anders LU and Boström, Anders (1984) In Geophysical Journal International 79(3). p.835-862
Abstract
The propagation of a pulsed elastic wave in the following geometry is considered. An elastic half-space has a surface layer of a different material and the layer furthermore contains a bounded 3-D inhomogeneity. The exciting source is an explosion, modelled as an isotropic pressure point source with Gaussian behaviour in time.



The time-harmonic problem is solved using the null field approach (the T matrix method), and a frequency integral then gives the time-domain response. The main tools of the null field approach are integral representations containing the free space Green's dyadic, expansions in plane and spherical vector wave functions, and transformations between plane and spherical vector wave functions. It should... (More)
The propagation of a pulsed elastic wave in the following geometry is considered. An elastic half-space has a surface layer of a different material and the layer furthermore contains a bounded 3-D inhomogeneity. The exciting source is an explosion, modelled as an isotropic pressure point source with Gaussian behaviour in time.



The time-harmonic problem is solved using the null field approach (the T matrix method), and a frequency integral then gives the time-domain response. The main tools of the null field approach are integral representations containing the free space Green's dyadic, expansions in plane and spherical vector wave functions, and transformations between plane and spherical vector wave functions. It should be noted that the null field approach gives the solution to the full elastodynamic equations with, in principle, an arbitrarily high accuracy. Thus no ray approximations or the like are used. The main numerical limitation is that only low and intermediate frequencies, in the sense that the diameter of the inhomogeneity can only be a few wavelengths, can be considered.



The numerical examples show synthetic seismograms consisting of data from 15 observation points at increasing distances from the source. The normal component of the velocity field is computed and the anomalous field due to the inhomogeneity is sometimes shown separately. The shape of the inhomogeneity, the location and depth of the source, and the material parameters are all varied to illustrate the relative importance of the various parameters. Several specific wave types can be identified in the seismograms: Rayleigh waves, direct and reflected P-waves, and head waves. (Less)
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author
publishing date
type
Contribution to journal
publication status
published
subject
in
Geophysical Journal International
volume
79
issue
3
pages
835 - 862
publisher
Wiley-Blackwell
external identifiers
  • scopus:84986412081
ISSN
0956-540X
DOI
10.1111/j.1365-246X.1984.tb02872.x
language
English
LU publication?
no
id
125e5f9e-d6e7-4d1a-88f2-68965e32f2d6 (old id 1038684)
date added to LUP
2008-02-27 14:37:39
date last changed
2017-07-30 04:51:30
@article{125e5f9e-d6e7-4d1a-88f2-68965e32f2d6,
  abstract     = {The propagation of a pulsed elastic wave in the following geometry is considered. An elastic half-space has a surface layer of a different material and the layer furthermore contains a bounded 3-D inhomogeneity. The exciting source is an explosion, modelled as an isotropic pressure point source with Gaussian behaviour in time.<br/><br>
<br/><br>
The time-harmonic problem is solved using the null field approach (the T matrix method), and a frequency integral then gives the time-domain response. The main tools of the null field approach are integral representations containing the free space Green's dyadic, expansions in plane and spherical vector wave functions, and transformations between plane and spherical vector wave functions. It should be noted that the null field approach gives the solution to the full elastodynamic equations with, in principle, an arbitrarily high accuracy. Thus no ray approximations or the like are used. The main numerical limitation is that only low and intermediate frequencies, in the sense that the diameter of the inhomogeneity can only be a few wavelengths, can be considered.<br/><br>
<br/><br>
The numerical examples show synthetic seismograms consisting of data from 15 observation points at increasing distances from the source. The normal component of the velocity field is computed and the anomalous field due to the inhomogeneity is sometimes shown separately. The shape of the inhomogeneity, the location and depth of the source, and the material parameters are all varied to illustrate the relative importance of the various parameters. Several specific wave types can be identified in the seismograms: Rayleigh waves, direct and reflected P-waves, and head waves.},
  author       = {Karlsson, Anders and Boström, Anders},
  issn         = {0956-540X},
  language     = {eng},
  number       = {3},
  pages        = {835--862},
  publisher    = {Wiley-Blackwell},
  series       = {Geophysical Journal International},
  title        = {Exact synthetic seismograms for an inhomogeneity in a layered elastic half-space},
  url          = {http://dx.doi.org/10.1111/j.1365-246X.1984.tb02872.x},
  volume       = {79},
  year         = {1984},
}