Attribute Description: The Envelope Breaks attribute calculates out the minima of the envelope and picks that minima. It helps isolate intervals in the seismic trace and can be useful in extracting block information between each break based on another attribute. A detailed explanation of Banded attributes is described in the Help document “Banded Attribute Overview”.
Interpretation Use: This attribute may provide value by
- Isolating unit boundaries
- Defining unit continuity
The data for this attribute is basically the spike that defines the pick location and zero. As seen in the amplitude spectrum, zero dominates the values and the remaining values are all the pick value so only two colors are really used. You just need to set the highest value as the color you want to highlight the picks.
Computation: Envelope breaks are picked on envelope minimums. They are computed in an almost an equivalent way to the way to picking peaks on phase breaks. Following the same steps as before, a single envelope trough pick of the envelope signal e(t) but with an underbrace to represent a trough pick is written.
The pick is a vector of two elements – pick time and envelope value. The trough is a point on the envelope curve where the first derivative is zero and the second derivative is negative. A picking level controls the number of picks. It sets the threshold of envelope as a number of decibels below the largest peak value of envelope of the signal. Below the threshold, troughs are not picked. The threshold is ignored and all envelope troughs are picked when the decibel range is set to zero.
The ordered set of all trough envelope picks is
which represents the list of all selected trough picks on the envelope signal. The number of picks
From this set of trough picks, an envelope spike signal of pick times is constructed with Kronecker delta functions.
The underbrace notation here represents a picked trough signal of spikes and is the time of the i-th pick.
This result is the envelope breaks attribute.
Note that since the picks were made on the Envelope of the trace – they don’t always coincide with a trough or peak of the real or amplitude trace. Phase picks do a better job of this. These breaks represent the minima of the energy of the trace as represented by the Envelope and have a different significance for interpretation.
- Taner, M. T., 2001, Seismic attributes: Canadian Society of Exploration Geophysicists Recorder, 26, no 7.
- Oliveros, R.B., and B. J. Radovich, 1997, Image-processing display techniques applied to seismic instantaneous attributes on the Gorgon gas field, North West Shelf, Australia; 67th Annual International Meeting, SEG, Expanded Abstracts, 2064-2067