In areas of complex geology, migration-velocity estimation should use methods that describe the complexity of wavefield propagation, such as focusing and defocusing, multipathing, and frequency-dependent velocity sensitivity. Migration-velocity analysis by wavefield extrapolation has the ability to address these issues because, in contrast to ray-based methods, it uses wavefields as carriers of...

Background: The cognitive bases of language impairment in specific language impairment (SLI) and autism spectrum disorders (ASD) were investigated in a novel nonword comparison task which manipulated phonological short term memory (PSTM) and speech perception, both implicated in poor nonword repetition. Aims: This study aimed to investigate the contributions of PSTM and speech perception in non...

The space-time Greens functions for 3-D poststack and 3-D prestack migration in a homogeneous medium are derived under the fareld approximation. These Greens functions can be used to practically compute synthetic migrated images. Examples are given for the recording footprint noise associated with a point scatterer and a meandering river channel. The Greens functions also provide fundamental in...

3-D prestack common-azimuth depth migration has a strong potential for imaging accurately complex media and handling multi-pathing. We apply the technique to North Sea real data for imaging a salt dome. The results obtained demonstrate the efficiency of the method in complex media. A detailed analysis of common-image gathers shows opportunities for improving the velocity model.

Prestack Stolt residual migration can be applied to seismic images that are depth migrated using wavefield extrapolation techniques. This method has significant advantages over other methods that estimate interval velocity functions for depth migration. It is more accurate than methods that are based on focusing the stack of migrated images by a residual NMO operation, so it provides a more acc...

Common-azimuth migration (CAM) is a 3-D prestack depth migration technique based on the wave equation (Biondi and Palacharla, 1996). It exploits the intrinsic narrow-azimuth nature of marine data to reduce its dimensionality and thus manages to cut the computational cost of 3-D imaging significantly enough to compete with Kirchhoff methods. Based on a recursive extrapolation of the recorded wav...

Strong refraction of waves in the migration velocity model introduces kinematic artifacts coherent events not corresponding to actual reflectors into the image volumes produced by prestack depth migration applied to individual data bins. Because individual bins are migrated independently, the migration has no access to the bin component of slowness. This loss of slowness information permits eve...

The common-focus-point technology CFP describes prestack migration by focusing in two steps: emission and detection. The output of the first focusing step represents a CFP gather. This gather defines a shot record that represents the subsurface response resulting from a focused source wavefield. We propose applying the recursive shot-record, depthmigration algorithm to the CFP gathers of a seis...