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Hi everybody,
Similar to my question about the Root Mean Square... What is Variance and how can I use it to visualise sedimentary bodies, like channels? thanks!

Vikesh,

The variance (the opposite of coherency) attribute is calculated in three dimensions and represent the trace-to-trace variability over a particular sample interval and therefore produces interpretable lateral changes in acoustic impedance. Similar traces produce low variance coefficients, while discontinuities have high coefficients. Because faults and channels may cause discontinuities in the neighboring lithologies and subsequently in the trace-to-trace variability they become detectable in 3D seismic volumes. Variance can thus be seen as the lateral counterpart of RMS as the later indicates vertical variations.

Deos that answer your question?

Thank you petrel_user. that is the answer I was looking for!

Hi Petrel user,
Could you please make it clear what you mean my 'calculated', what is to be calculated, is the acoustic impedance or amplitude,..?
And also as it is calculated in 3D so the results are expected to see the changes in acoustic impedance laterally and vertically?
Thanks much

Actually variance only highluights vertical variations in accoustic impedence. It compares traces next to each other at each sample position. If there's a differnece it's probably due to a fault or a channel (amongst noise of course)