Source directivity and its effects on resolution and signature deconvolution

Abstract

After a brief discussion on why source patterns are now an integral part of marine acquisition parameters the argument is developed that these very same arrays inhibit the response of high frequencies with offset, even at depth, which cannot be restored even if signature deconvolution takes source directivity into account. A controlled experiment is described where the only variable is the critical 'in-line' dimension of the source pattern. The source in this case was waterguns but it could equally have been sleeve airguns or marine vibroseis, each with enough bandwidth to demonstrate the effects revealed in this paper. Raw field records are compared by exclusive filter suites, normalised onto each other, up to the limit of the 4 ms anti-alias filter. Thereafter signature deconvolution is compared, again on the same field records, but over a short single cover section of constant offset, in the first case from the middle of the streamer, around 1500 m offset and in the second case near the end of the streamer approximately 3000 m offset.