Figure 1

Dispersion error curves for the different implicit SGFD schemes. The time step is 2.5 ms and the spatial grid interval is 20 m. (a) The implicit SGFD scheme with v = 1500 m/s; (b) the implicit SGFD scheme with v = 4500 m/s; (c) the HEI-SGFD scheme with v = 4500 m/s; (d) the HEI-SGFD scheme with v = 4500 m/s.