[OpendTect_Users] Instantaneous frequency map interpretation

[Friso Brouwer]

Hello Yoon, Keun,

I did not see a map attached to your email, so it hard to qualify the
feature you are looking at.

That said, anomalies in the instantaneous frequency that are far out of the
range of the frequency bandwidth (and may also be negative) are normal, and
related to reflections from thin beds. Without going in all mathematical
details, the interference of the top and bottom reflection from a thin bed
cause an artifact or anomaly in the instantaneous frequency. Often we can
use that effect to our advantage to detect the presences of thin layers, an
application of this principle is Tury Tanner's thin bed indicator.  This
may also be what you are picking up, if your extraction look geological
plausible.

As these anomalies may be very thin in time dimension, make sure they are
snapped correctly to a horizon, and you see a true geological
representation of the feature. If there is not a perfect alignment between
horizon and attribute, this can be corrected using the Volume Statistics
attribute, with the instantenous frequency as input, a short time window,
and the extreme value statistical option. This will snap anomalies that are
just above/below the horizon back to the horizon...

I hope this helps.

Cheers,

Friso

On Wed, Jul 25, 2012 at 10:39 AM, Yoon keun <geophysics.lab.md at gmail.com>wrote:

> Dear all,
>
> I would just like to ask how to interpret maps of instantaneous frequency
> attribute in OpendTect.
>  Basically, the attribute outputs the instantaneous frequency at the
> sample location. My data has an effective bandwidth of 10 to 80 Hz; however,
> the frequency map reveals interesting features when frequency reaches 2500
> (0-2500 interval on color bar).
>
> Thank you very much in advance for any help.
>
> Best regards.
>
> Yoon keun
> Chonnam University
> South Korea
>
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