Translations:Implementation of migration/9/en

We obtain Table 3 by adding Tables 1 and 2 entry by entry. Table 3 gives the two-way traveltimes. For example, the traveltime from source (1, 3) to depth point (4, 6) and back to receiver (1, 11) is $t\left({\rm {4,6}}\right){\rm {=4.24+5.83=}}{\rm {10.07}}$. This number (rounded) appears in the fourth row, sixth column of Table 3. A contour map of Table 3 would reveal that the contour lines are elliptical curves of constant two-way traveltime for the given source and receiver pair.