Discrete point-source tensor g_αν^m;h for one crack, computed using the staggered-grid FD operator. The crack is situated in the origin and is oriented along the x-axis. The half-width of the crack, a_m, is given by a_m= 0.5 m. The grid spacing is 2 m. The area around the crack, necessary to represent it as a distributed point source, is typically chosen as a square containing 7 × 7 grid cells.