1.7 Anomalous Amplitude Replacement

1.7 Anomalous Amplitude Replacement and Attenuation Anomalous frequency bands can be either attenuated or replaced with interpolated data. If FREQ_REPLACE_INTERP is selected, noisy frequency bands are replaced by a weighted average of the real and imaginary complex frequencies. The average is computed using the two closest traces that are not anomalous, one on each side of the anomalous trace. The weights are based on the trace distance (number of traces) from the anomalous trace, and the sum of the weights always equals 1. For example, if the traces used for interpolation are 1 and 3 traces from the noisy trace, their complex values are multiplied by .75 and .25 respectively; traces 2 and 3 trace distances are weighted by .6 and .4, respectively. If the traces used for interpolation are the same distance from the noisy trace (say 2 traces), they are each given equal weights of .5. The sum of the weighted complex values replaces the anomalous frequency values. The FREQ_REPLACE_INTERP_APERTURE_MAX parameter defines the trace distance limit for interpolation. The default value for this parameter is 3 traces. If two non-anomalous traces cannot be found within this number of traces, one on each side of the noisy trace, the trace cannot be interpolated and is attenuated by the factor specified by the ATTEN_FACTOR parameter. Therefore, any anomalous frequency bands in the first or last trace of the gather is always attenuated rather than interpolated.