I am pleased that Vermeer finds my paper on finite-difference (FD) modeling to be interesting. However, from his comments regarding my use of reciprocity to design wide-azimuth towed-streamer (WATS) surveys, it is apparent that I failed to explain that point clearly and thereby caused unnecessary confusion. Let me try again.

Vermeer states that I assume it is unnecessary to acquire shot-receiver azimuths in all four quadrants because reciprocity would make such measurements redundant. He further states that I use that assumption as the rationale to model and acquire data in only two shot-receiver azimuth quadrants. This is incorrect. Referring to Figure 10 in Regone (2006), I stated: “If we ignore the edges of the 3D survey, and we have sources everywhere we have receivers, we can use reciprocity to eliminate the left half of the receiver patch as shown in Figure 10b.”

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