COHERENCE ATTRIBUTE
- Measurement of similarity among the seismic traces/wavelets
- calculate localised waveform similarities in both in-line and cross-line
Why use coherence?
Methods of measuring coherence
Cross - correlation based coherence
- sensitive to waveform
- operates in 3 neighbouring traces (2 targets, 1 master)
- value = 1 = high coherence
Semblance based coherence
i) Define space and a time aperture
ii) Define dip and azimuth for each point
iii) Calculate ratio of energy of all the traces along a specified dip
iv) Measure degree of similarities to each other of all the traces along the selected dip within the selected square or elliptical outline
v) might include noise and low frequency unwanted data
Variance based coherence
> most popular
> almost identical to semblance method
> Variance = 1 - semblance estimate coherence
> measure of how well each trace fits the mean trace
> if all traces are identical/similar = 0
> if all traces are identical but of different amplitude = > 0
Coherence enhances :
* Faults and fracture system
*Channels
*Edge detection
*Other geological features
THANK YOU
