Exact synthetic seismograms for an inhomogeneity in a layered elastic halfspace
(1984) In Geophysical Journal International 79(3). p.835862 Abstract
 The propagation of a pulsed elastic wave in the following geometry is considered. An elastic halfspace has a surface layer of a different material and the layer furthermore contains a bounded 3D inhomogeneity. The exciting source is an explosion, modelled as an isotropic pressure point source with Gaussian behaviour in time.
The timeharmonic problem is solved using the null field approach (the T matrix method), and a frequency integral then gives the timedomain 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 halfspace has a surface layer of a different material and the layer furthermore contains a bounded 3D inhomogeneity. The exciting source is an explosion, modelled as an isotropic pressure point source with Gaussian behaviour in time.
The timeharmonic problem is solved using the null field approach (the T matrix method), and a frequency integral then gives the timedomain 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 Pwaves, and head waves. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/record/1038684
 author
 Karlsson, Anders ^{LU} and Boström, Anders
 publishing date
 1984
 type
 Contribution to journal
 publication status
 published
 subject
 in
 Geophysical Journal International
 volume
 79
 issue
 3
 pages
 835  862
 publisher
 WileyBlackwell
 external identifiers

 scopus:84986412081
 ISSN
 0956540X
 DOI
 10.1111/j.1365246X.1984.tb02872.x
 language
 English
 LU publication?
 no
 id
 125e5f9ed6e74d1a88f268965e32f2d6 (old id 1038684)
 date added to LUP
 20080227 14:37:39
 date last changed
 20170917 08:21:08
@article{125e5f9ed6e74d1a88f268965e32f2d6, abstract = {The propagation of a pulsed elastic wave in the following geometry is considered. An elastic halfspace has a surface layer of a different material and the layer furthermore contains a bounded 3D inhomogeneity. The exciting source is an explosion, modelled as an isotropic pressure point source with Gaussian behaviour in time.<br/><br> <br/><br> The timeharmonic problem is solved using the null field approach (the T matrix method), and a frequency integral then gives the timedomain 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 Pwaves, and head waves.}, author = {Karlsson, Anders and Boström, Anders}, issn = {0956540X}, language = {eng}, number = {3}, pages = {835862}, publisher = {WileyBlackwell}, series = {Geophysical Journal International}, title = {Exact synthetic seismograms for an inhomogeneity in a layered elastic halfspace}, url = {http://dx.doi.org/10.1111/j.1365246X.1984.tb02872.x}, volume = {79}, year = {1984}, }