Seismic Data ProcessingLecture 14

Stacking and migration

Dr Amin KhalilSchool of Physics, USM

Huygen’s principle

Huygen’s principleWave diffraction

Wave Diffraction Example

Back to Migration

The time for a diffracting point located at (xd , Zd ) is given by:

This equation represent hyperbola like the one seen at the following figure.

This figure shows the diffractor to the left and its corresponding time on the zero offset seismic section.

Diffraction stacking Cont’d

In early days, Before the computer era, people used stacking along the hyperbola in order to obtain the diffraction point. This require the knowledge of the velocity to carry out stacking. In case that we have more than one diffraction point with different velocities we apply stacking for each hyperbola with its proper stacking velocity.

Diffraction stacking Cont’d

In early computer age the following relation is used:

In the preceding slides we dealt with single point diffraction. This principle can be further used to image the whole refractor by consider all other diffractor point. When the separation between diffraction points become infinitesimally small, the reflector is then determined (Huygen’s principle).

An example of this is shown in the next slide, where the concept is applied to four diffraction points.

Four points diffractor

If the points separation is infinitely small, a reflector then can be mapped.

Dipping reflector

In the present case the migration is applied by multiplying by 1/cos q, where q is the dip angle. As illustrated in the following fig.

Bow-tie phenomena

Assignment

Crack.seismo.unr.edu/jrg/

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assignment

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