Migration velocity analysis (MVA) in depth (Reshef, 1992) has been successfully applied to P-P data, especially in structural areas where stacking velocity analysis fails. In this paper, the migration velocity analysis technique is investigated in time and is applied to P-S seismic data. This technique is slightly modified for the asymmetrical raypaths of converted wave data. It is assumed that, before the MVA, the P-wave RMS velocity function is known from P-P processing. The RMS Vp/Vs value, γ rms , is introduced during the MVA. This time-and-space variant γ rms function is sought rather than the RMS velocity function for S-wave itself during the velocity analysis. However the γ rms value and S-wave velocity are convertible.
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