Converted-wave ͑PS͒ data, when converted to PP time, develop time-and location-varying compression of the seismic wavelet due to a variable subsurface ␥ ͑␥ ס Vp / Vs͒. The time-dependent compression distorts the wavelet in a seismic trace. The lack of a consistent seismic wavelet in a domainconverted PS volume can eventually lead to an erroneous joint PP/PS inversion result. Depth-converted seismic data also have wavelet distortion due to velocity-dependent wavelet stretch. A high value of seismic velocity produces more stretch in a seismic wavelet than a low value. Variable wavelet stretch renders the depth data unsuitable for attribute analysis. A filtering scheme is proposed that corrects for distortion in seismic wavelets due to domain conversions ͑PS to PP time and time-to-depth͒ of seismic data in an amplitude-preserving manner. The method uses a Fourier scaling theorem to predict the seismic wavelet in the converted domain and calculates a shaping filter for each time/depth sample that corrects for the distortion in the wavelet. The filter is applied to the domain-converted data using the method of nonstationary filtering. We provide analytical expressions for the squeeze factor  that is used to predict the wavelet in the converted domain. The squeeze factor  for PS to PP time conversion is a function of the subsurface ␥ whereas for PP timeto-depth conversion  is dependent on subsurface P-wave velocity. After filtering, the squeezed wavelets in domainconverted PS data appear to have resulted from a constant subsurface ␥ , which we denote as ␥ rep . Similarly, the filtered depth-converted data appear to have resulted from a constant subsurface P-wave velocity V rep .
Eleven years ago, publication of the UK North Sea Alba Field OBC converted-wave (PS) image examples by MacLeod et al. caused quite a stir. The authors provided convincing evidence that “the Alba survey is the first 3D OBC survey in which successful converted-wave imaging of the reservoir has created significant economic benefit.” Most of us with an interest in multicomponent seismology know it well, as Alba has become one of the classic examples of a “stealth” reservoir (Rape et al., 2005), having low P- but high S-impedance contrast. The Alba reservoir and others like it are difficult to recognize on conventional P-wave images, but they stand out quite nicely when viewed on their PS equivalents.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.