The Leading Edge; May 2002; v. 21; no. 5;
p. 438-444; DOI: 10.1190/1.1481249
© 2002 Society of Exploration Geophysicists
Lena
A seismic model
Dave Monk
Apache Corporation, Houston, Texas, U.S.
Corresponding author: David.Monk@usa.apachecorp.com
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In the May 2000 issue of TLE, Chris Liner raised the issue of available bandwidth in seismic data and suggested that it is the lack of low frequencies in recording which limits our ability to properly image the subsurface. In this entertaining article, Liner uses a standard image, Lena, to demonstrate what happens to a familiar image when we lose the high and low frequencies and suggests that perhaps the poor response of geophones to low frequencies is a problem. Those who attended SEG's 2001 Annual Meeting in San Antonio had the opportunity to experiment with "LenaSeis" at the convention and look at the impact of different high and low frequency limits.
Figure 1, taken from Liner's article, illustrates his point. The premise is that "real" images contain all wavenumbers and frequencies, but that seismic images are degraded through loss of high and low frequencies. Liner says that although we might expect "to do a much better job imaging low dip features (bedding surfaces) than steep dip features (faults)", the problem is intrinsic and caused by the low-frequency limitation of seismic (at the recording stage). He then goes on to point out that inversion attempts to restore some missing low frequencies.
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Figure 1. Lena, as seen by Liner.
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However, the analysis suggested by Liner appears to overlook one aspect of the seismic experiment; i.e., the data that are recorded are not the final image and we know that seismic data must at least pass through the step of migration. Because migration intrinsically lowers the frequency of dipping events, might it be possible that low-frequency limitations in the recording instruments are somewhat compensated by the frequency-lowering effects of migration? Might we expect to image steep-dip features in a more broadband way than low-dip features because low frequencies can be recovered for . . . [Full Text of this Article]
Copyright © 2009 by Society of Exploration Geophysicists
