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Figure 3 shows the impulse response of prestack slant stack migration
with PSPI, with *p*=.00021 s/m, *v*_{1}(*z*)=1500+0.5*z* m/s at *y*=0 m, and
*v*_{2}(*z*)=2500+0.5*z* m/s
at *y*=2560 m. The skewed impulse responses are caused by
the velocity variations in depth and in lateral variation.
To test the accuracy of the PSPI operator, I used *v*_{1}(*z*)=1500 m/s
at *y*=0 m and *v*_{2}(*z*)=2500 m/s at *y*=2560 m to simulate the response of
*v*=2000 m/s at *y*=1280 m. Figure 4 shows these two impulse responses together.
The impulse response with a wider aperture is from the PSPI, and the other is the
response with *v*=2000 m/s. The bottom of the responses coincide very well,
even with the velocity discrepancy. By increasing the velocity discrepancy,
we get Figure 5, with *v*_{1}(*z*)=1000 m/s and *v*_{2}(*z*)=3000 m/s. The
bottom of the responses are no longer coincident, and the discrepancy
gets worse as the depth increases.

**fig3
**

Figure 5 The superposition of the impulse response of *v*=2000 m/s and *v*_{1}(*z*)=1000
m/s at *y*=0 m and of *v*_{2}(*z*)=3000 m/s at *y*=2560 m with PSPI.

** Next:** CONCLUSION
** Up:** Lin: Prestack PSPI
** Previous:** Two-pass PSPI
Stanford Exploration Project

11/17/1997