# Dictionary:Trace envelope

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The trace envelope is a seismic attribute, also known as *instantaneous amplitude,* is a representation of the
amplitude of an oscillatory function . The quantity is of the same order as the absolute value of the amplitudes of the function. Instantaneous amplitude varies approximately between 0 and the absolute value of the maximum amplitude of the trace.

The envelope of seismic signals is independent of the phase and may be related directly to a variety of other trace attributes. The trace envelope of a seismic signal may represent the individual interface contrast or, the combined response of several interfaces, depending on the seismic bandwidth.^{[1]}

The instantaneous amplitude of a seismic trace is related to a form of the trace called the analytic trace, which is the representation of the original seismic trace as a complex-valued function . Thus the trace amplitude is given by the modulus at each time

.

Here, the real part of the analytic trace , is just the original seismic trace .
The imaginary part , also called the *quadrature trace,* is computed by taking the *Hilbert transform* of .

The trace envelope is a physical attribute and can be used as an effective discriminator for the following characteristics:

- Is proportional to the the acoustic impedance contrast, hence is related to reflectivity
- Bright Spots
- Possible gas accumulation
- Sequence boundaries
- Thin-bed tuning effects
- Unconformities
- Major changes in lithology
- Major changes in depositional environment
- Lateral changes indicating faulting
- Spatial correlation to porosity and other lithologic variations.

## References

- ↑ Taner, Turhan (1992), Attributes Revisited, Rock Solid Images Houston, Texas (published 2000)