Abstract:The velocity of reflection event from a reflector may vary with offsets under the conditions of complex structure and inhomogeneous medium so that the reflection event is not in hyperbolic form.As a result,NMO correction using stack velocity function V (T0)can not thoroughly remove moveout,and stack effect will be unsatisfactory. It is discussed how the hyperbolic time-distance curve of reflection wave is influenced by overlying-layer velocity variance and reflector undulation,Non-hyperbolic normal moveout correction,abbreviated to NHNMO,includes these essential:(1)using the concept of ray average velocity V (T0 ,x),(2) replacing V(T0 )in normal moveout (ΔT) formula by V(T0 ,x),(3)obtai.nxnent of ray average velocity by calculating residual NMO correction value ΔΔT,and (4)moving whole objective reflection segment to avoid waveform distortion.It has been shown that both the reflection events of trace gather and stacked seismic section which were obtained using NHNMO correction are better than those obtained using conventional NMO correction.