Abstract：
Serious stretch appears in shallow long offset signals after NMO correction.In this article we study the generation mechanism of NMO stretch, demonstrate that the conventional travel time equation cannot accurately describe the travel time of the samples within the same refl ection wavelet. As a result, conventional NMO inversion based on the travel time of the wavelet’s central point occurs with errors. In this article, a travel time equation for the samples within the same wavelet is reconstructed through our theoretical derivation (the shifted fi rst arrival point travel time equation), a new NMO inversion method based on the wavelet’s fi rst arrival point is proposed. While dealing with synthetic data, the semblance coeffi cient algorithm equation is modifi ed so that wavelet fi rst arrival points can be extracted. After that, NMO inversion based on the new velocity analysis is adopted on shot offset records. The precision of the results is signifi cantly improved compared with the traditional method. Finally, the block move NMO correction based on the fi rst arrival points travel times is adopted on long offset records and non-stretched results are achieved, which verify the proposed new equation.
TAN Chen-Qing,WU Yan-Gang,HAN Li-Guo et al. Shifted first arrival point travel time NMO inversion[J]. APPLIED GEOPHYSICS, 2011, 8(3): 217-224.
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2011, Vol. 8 
