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Challenges of complex media

Landmark Graphics, Denver, Colorado, U.S.

Martijn de Hoop

Colorado School of Mines, Golden, Colorado, U.S.

Corresponding author: slevin@lgc.com

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

The third session of the 2001 SEG Summer Research Workshop on "Synergies in Geophysical, Medical, and Space Imaging" discussed imaging in complex media—a challenge in all sciences. Just consider imaging the living human body where parts are always moving! Presentations in this session focused on imaging applications in which the big challenge is to create an image, rather than to extract quantitative information from the image.

	Reverse-time medical and seismic imaging

 
Because of circumstances outside of anyone's control, keynote speaker Mathias Fink of the Laboratoire Ondes et Acoustic, ESPCI, University Denis Diderot had to cancel his talk on medical imaging via time-reversed acoustics. This was unfortunate as time-reversed acoustics is an excellent example of an imaging technique that has had some striking achievements in research. This acoustic technique focuses as much transmitter energy as possible on a target region in order to maximize locality and signal-to-noise ratio in the resulting image. In the geophysical world, time-reversed acoustics has parallels in the early work of Schultz and Claerbout (1978)—and later Rietveld, Berkhout and Wapenaar (1992)—in which plane wave imaging was generalized to beamforming according to the arrival times and amplitudes of reflectors and point diffractors. It also has parallels in reverse-time seismic imaging, wherein zero-offset data are time-reversed and propagated back into a model of the subsurface in order to create an image. Fink's approach goes a step farther by using time-reversed recorded signals from the actual experiment as the generalized beams rather than approximating the beams by calculations from a model of the target to be illuminated. This powerful approach has generated a lot of excitement in the geophysical imaging community, and we eagerly anticipate its application to subsurface imagery.

	Elastic imagery: seismic, environmental, and medical applications

 
Robert Godfrey, WesternGeco, started the session with recent results and future challenges in multicomponent imaging of elastic waves in the marine environment. Figure 1 summarizes . . . [Full Text of this Article]