Calculating Dominant Frequency per Horizon

[Nadhira Rahmani Zulkarnain]

Dear OpendTect Users,

I have a question regarding the calculation of dominant frequency per horizon in OpendTect. I understand that we can visualize dominant frequency using Display > Amplitude Spectrum on a seismic volume. However, I would like to know if there is a way to perform this calculation per horizon, rather than per millisecond in the seismic cube.

Is there a specific workflow that allows for this type of frequency analysis? Any guidance or suggestions would be greatly appreciated.

Thank you in advance for your help!

Best regards, 

Nadhira Rahmani Zulkarnain

[Paul de Groot]

Dear Nadhira,

Dominant Frequency is an option of the Frequency attribute (see image). This means you first have to define this attribute in the (3D) attribute engine. Next you add the horizon and add a new attribute layer in which you apply the attribute you just defined. More about attribute analysis can be found in various videos on the dGB website, e.g. 

• OpendTect Technology Webinar (2023): Unlock the potential of OpendTect's Attribute Engine
• OpendTect Technology Webinar (2020): Data enhancement - a short demo of attributes, filters, testing and QC

Best regards,

Paul.

--

Paul de Groot

Special Adviser

-----------------------------------------------------------------------------------------------------------------------   dGB Earth Sciences
Phone: +31 53 4315155 E-mail: paul.d...@dgbes.com Internet: dgbes.com

----------------------------------------------------------------------------------------------------------------------- 

--
You received this message because you are subscribed to the Google Groups "OpendTect Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to users+un...@opendtect.org.
To view this discussion visit https://groups.google.com/a/opendtect.org/d/msgid/users/72fbb442-6fa9-4446-b26f-b1b891703acen%40opendtect.org.

[Nadhira Rahmani Zulkarnain]

Dear Paul,

Thank you for your kind response. I realize I may not have been entirely clear in my previous message. What I intended to ask was how to determine the value of the dominant frequency within a seismic interval bounded by two horizons, rather than visualizing a dominant frequency map on a single horizon.

I'm a bit confused because, to my knowledge, the only way to determine the dominant frequency value is through the seismic cube using Volume > Display > Amplitude Spectrum.

Could you kindly clarify if there’s an alternative method to extract the dominant frequency specifically for the seismic interval between two horizons?

Best regards,

Nadhira

[Paul de Groot]

Hi Nadhira,

To compute the dominant frequency on a horizon slice, I would build an attribute set that sets all values above horizon 1 and below horizon 2 to undefined values. This can be done with two horizon attributes that output the Z value of the horizons and a mathematics attribute that compares the actual Z position with the Z values of the horizons. The output of the mathematics attribute is the input of the dominant frequency attribute. Set the time-gate of the frequency attribute such that when you calculate it on a time-slice through the middle of the horizon slice, the entire interval is always captured. Let's assume the top of horizon 1 is at 1500 ms and the deepest value of the base horizon is at 2500 ms. Then you can compute the Dominant Frequency with a time-gate of [-500,+500] ms on a time-slice at 2000 ms.

The way to prepare the input with horizon attributes and the mathematics attribute has been described in a previous chain on this mailing list, see https://groups.google.com/a/opendtect.org/d/msgid/users/CA%2Br_Z34wfkocZCJLtKN9y9R-yocBvC-etk77n4CKuj%3DcVR3RcQ%40mail.gmail.com

Best regards,

Paul.

--

Paul de Groot

Special Adviser

-----------------------------------------------------------------------------------------------------------------------   dGB Earth Sciences
Phone: +31 53 4315155 E-mail: paul.d...@dgbes.com Internet: dgbes.com

-----------------------------------------------------------------------------------------------------------------------