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Hatchell (2000a) proves using both real and synthetic
data that FEAVO effects can be generated not only by shallow velocity
anomalies, but also by deep ones. Figure 7 reproduces the
forward modeling in Hatchell (2000a). A pseudospectral
wave propagation algorithm Biondi (2002) is used to
produce the wavefield recorded at a depth of 6000m. Ignoring the
dispersion effects, the bottom two
panels in the figure exhibit a striking quantitative similarity to the
results in Hatchell (2000a) and emphasize that
deep-origin FEAVO effects exist, and that they can be modeled numerically.
**hatsim
**

Figure 7 Left, from top to bottom:
1. Downward continuation of a shot from surface to 6 km deep, with constant
velocity. 2. Downward continuation through upper right velocity model.
3. Difference between 1 and 2. Right, from top to bottom: 4. New
velocity model -- homogenous with a lower velocity slab
inserted. 5. Difference between the maximum amplitudes in panel 1 and
panel 2, for each x location. 6. Difference between the times of the
maximum amplitudes in panels 1 and 2, for each x location.

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Stanford Exploration Project

6/7/2002