The space-time Greens functions for 3-D poststack and 3-D prestack migration in a homogeneous medium are derived under the far-field 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...

This paper presents a method of Stolt residual migration applicable to prestack data. The method’s main merit is that instead of requiring an assumption about the magnitude of the new velocity model to which we want to residually migrate, it only calls for an assumption about the ratio of the reference velocity to the new one. Since the method is, in essence, a Stolt-stretch technique, it inher...

Common-azimuth migration (CAM) is an attractive solution for 3-D prestack imaging. It reduces the full 5-D phase-shift operator to 4-D through the stationary-phase approximation, lowering the computational cost. However, this assumption yields constraints in the downward-continuation process that can limit accuracy. Those errors are estimated in this paper by comparison to other wave-equation m...

Wavefields are commonly computed in the Cartesian coordinate frame. Its efficiency is inherently limited due to spatial oversampling in deep layers, where the velocity is high and wavelengths are long. To alleviate this computational waste due to uneven wavelength sampling, we convert the vertical axis of the conventional domain from depth to vertical time or pseudo depth. This creates a nonort...

Traveltime computation is an important part of seismic imaging algorithms. Conventional implementations of Kirchhoff migration require precomputing traveltime tables or include traveltime calculation in the innermost computational loop . The cost of traveltime computations is especially noticeable in the case of 3-D prestack imaging where the input data size increases the level of nesting in co...

Traveltime computation is an important part of seismic imaging algorithms. Conventional implementations of Kirchhoff migration require precomputing traveltime tables or include traveltime calculation in the innermost computational loop . The cost of traveltime computations is especially noticeable in the case of 3-D prestack imaging where the input data size increases the level of nesting in co...

In this report, we introduce a new wave-equation method of migration velocity analysis (MVA). The method is based on the linear relation that can be established between a perturbation in the migrated image and the generating perturbation in the slowness function. Our method consists of two steps: we first improve the focusing of the migrated image and then iteratively update the velocity model ...

A common problem in seismic tomography is the inadequate amount of data required for accurate traveltime inversion. The inherent nature in which data is acquired and the subsurface velocities of the survey area can result in a nonuniform distribution of raypaths. In such instances the statistical nature of tomographic inversion biases the solution to reflect the acquisition instead of the geolo...