paul sava

Extended imaging conditionsA typical imaging condition for seismic reflection data involves source and receiver wavefield matching, e.g. by crosscorrelation, at every image location. This statement is true no matter how the two wavefields are reconstructed, for example by oneway wavefield extrapolation, or twoway reversetime extrapolation, or Kirchhoff integral methods. This statement is also true when the source and receiver wavefields are reconstructed using different velocity models, as is the case for imaging of converted waves. Angledependent reflectivity information can be extracted from the source and receiver wavefield by retaining multiple lags of the imaging crosscorrelation, i.e. by analyzing the match of wavefields shifted relative to oneanother. Wavefields can be shifted in space (3D) or in time (1D), and each shift method has an associated angledecomposition method. This paper explores the various types of imaging condition using space and time shifts and derives relations for angle decomposition for convertedwave imaging using timeshifts. Migration with correct velocity: seismic image (left) spacelags image (center) timelags image (right) Migration with incorrect velocity: seismic image (left) spacelags image (center) timelags image (right) ReferencesSava, P.C., Fomel, S., 2003, Angledomain commonimage gathers by wavefield continuation methods, Geophysics, v. 68, no. 3, pp. 10651074 (PDF)Sava, P.C., Fomel, S., 2006, Timeshift imaging condition in seismic migration, Geophysics, v. 71, no 6, pp. S209S217. (PDF)
