Figure 4. This plot illustrates the magnitude of changes required of the raw sonic log (red curve in left track) to tie fully to the seismic data (final sonic is blue in left track). The drift between the edited sonic log and seismic data is shown in blue in the right track (scaled from -20 to +20 ms). The red dotted line indicates that we have two separate calibrations to make. The break in drift slope occurs at a run splice, hence the need to treat separate runs individually. The green curve in the right track shows the final time errors in the tied synthetic seismogram (typically less than 3 ms).