Figure 18. a) Synthetic seismogram of the Harris #1 well generated with a time varying zero phase Butterworth filter and both the sonic and density logs. The Butterworth filter has the following characteristics: 20 Hz, 36 dB/octave slope - 60 Hz, 72 dB/octave slope down to 500 ms; 20 Hz, 36 dB/octave slope - 50 Hz, 72 dB/octave slope from 500 ms to the bottom. Both negative and positive polarity synthetics are shown with the sonic log. Correlation tops include MRRW (Morrow clastic interval) and MISS (Mississippian limestone). b) Correlation of normal polarity synthetic with Line 2 (migrated section with reverse of field polarity and every other trace displayed). Well location indicated by thick, black vertical line.