Gain is a time-variant scaling in which the scaling function is based on a desired criterion. For instance, geometric spreading correction is applied to compensate for wavefront divergence early in processing, before deconvolution. Also before deconvolution, an exponential gain may be applied to compensate for attenuation losses. Often, gain is applied to seismic data for display. An automatic gain control (AGC) is applied to seismic data to bring up weak signals. Gain must be used with care, since it can destroy signal character. For example, an instantaneous AGC with a very small time gate makes strong reflections indistinguishable from weak reflections.
Unlike a gain function, trace balancing is a time-invariant scaling of amplitudes. Trace balancing usually is based on rms-amplitude criterion. Specifically, each trace in a group of traces is scaled so that they all have the same desired rms amplitude level.
- Geometric spreading correction
- Programmed gain control
- Rms amplitude AGC
- Instantaneous AGC
- Relative trace balancing
- A mathematical review of the Fourier transform