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

  1. Taner, Turhan (1992), Attributes Revisited, Rock Solid Images Houston, Texas (published 2000)