Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Vesnaver, A. Articles by Böhm, G. Search for Related Content GeoRef GeoRef Citation

Staggered or adapted grids for seismic tomography?

OGS, Trieste, Italy

Corresponding author: avesnaver@ogs.trieste.it

The first 20% of the full text of this article appears below.

Often a prisoner can see the sky from jail only through a grid. Thus, the grid may hide the moon or some landscape detail. In this case, he can solve the problem by moving his head just a bit. He will lose some other detail but will see the desired one. Because he remembers details seen before, his mind can reconstruct the image he would get out of the jail—without the grid. Actually, there is another way for reducing the grid annoyance; he could stretch the grid so that it does not hide any interesting view. However, this is more difficult (and less legal) and is usually adopted for other goals (e.g., escapes).

Seismic tomography lets geophysicists see down into the earth's interiors but through a grid. This grid is mathematical. Geophysicists estimate rock parameters along a fixed (often regular) pattern, meaning they may miss details poorly matched by that particular pattern. Unlike the prisoner, however, they rarely move their viewpoint or stretch the grid, although this is perfectly legal for them. We show here that both are readily available to geophysicists for a better view of the earth's interior properties.

	Staggered grids

 
A simple model for representing the earth is dividing it into regular blocks (the voxels), assumed to be internally homogeneous. The actual earth is much more complex, but we can estimate some local property (e.g., P-wave velocity) in the geologic formations, although it is averaged within the voxel. This averaging effect may mask little inhomogeneities, irregular boundaries between different rocks, slow velocity changes, and so on. Also, there are physical limits to achievable image resolution. However, the grid resolution supported by the data could be even lower. Thus, we can miss a few details just because of an unlucky choice of the shape, resolution, and position of the . . . [Full Text of this Article]