Conventions: Structure of Gxxxx matrix

The convention is to have the first N_shots columns correspond to source positions. The remaining N_traces columns correspond to the geophone stations. In our problem, there are 2 shot records, so the first two columns of G0003 are for shots 10 and 11 (because that was the order they were specified when running bref). The remaining columns correspond to geophone stations in the order the traces are read from the *.seg files. The last column is the horizontal distance between the source and receiver. The following matrix equation illustrates the setup for a very small problem (just for illustration, 2 shots, 3 geophones):

$$\left[\begin{array}{cccccc} 1 & 0 & 1 & 0 & 0 & x_{11}\\ 1 & 0 &... ...{c} t_{11}\\ t_{12}\\ t_{13}\\ t_{21}\\ t_{22}\\ t_{23}\end{array}\right],$$ (34)

where the shot delay times are $T_{s_{j}}$ and the geophone location delay times are $T_{g_{j}}$ . The refracted, first arrival times are indicated as $t_{sr}$ for the s-r shot and receiver pair, and the offset between the s-r shot-receiver pair is also subscripted as $x_{sr}$ .