The effect of subsurface sampling on one-dimensional synthetic seismograms; discussion and reply

In one part of their paper, Schoenberger and Levin describe time delays measured between specified phases of the transmitted wavelet and the calculated traveltime of the first onset. They point out that this time delay depends upon the time sampling, and it increases if the sample interval is decreased from 4 to 12 msec. The proper traveltime to compare to it, in our opinion, is not the traveltime of the first onset calculated by summing transit times, but the traveltime of the selected phase calculated with infinitely small sample intervals. Calculating time delays in this way, the time delay decreases with decreasing sample interval as the time delay between synthetic seismograms, and field seismograms decrease by calculating the synthetic ones with smaller sample intervals.