Nonlinear pairwise alignment of seismic traces

Abstract

Seismic trace alignment is a recurring need in seismic processing and interpretation. For global alignment via static shift, there are robust tools available, including crosscorrelation. However, another kind of alignment problem arises in applications as diverse as associating synthetic seismograms to field data, harmonizing P‐ and S‐wave data, residual NMO, and final multilevel flattening of common image gathers. These cases require combinations of trace compression, extension, and shift—all of which are time variant. The difficulty is to find a mapping between the traces that is in some senseoptimum. This problem is solved here using a modified form of the Needleman‐Wunsch algorithm, a global optimization method originally developed for aligning amino acid sequences in proteins. Applied to seismic traces, this algorithm provides a nonlinear mapping of one seismic trace onto another. The method extends to multitrace alignment since that problem can be broken down into a cascade of pairwise alignments. Seismic implementation of the Needleman‐Wunsch algorithm is a promising new tool for nonlinear alignment and flattening of seismic data.