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.
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
- Major changes in lithology
- Major changes in depositional environment
- Lateral changes indicating faulting
- Spatial correlation to porosity and other lithologic variations.
- Taner, Turhan (1992), Attributes Revisited, Rock Solid Images Houston, Texas (published 2000)