Seismograms of |${v}_z$| at the six receivers. In Fig. 7 (a) and (b), the solid lines represent the seismograms calculated by the FDM. The triangles and circles represent the seismograms calculated by the conventional LSM and the MDLSM, respectively. In Fig. 7 (c) and (d), the two solid lines represent the differences of seismograms for the conventional LSM and the MDLSM compared with the FDM, respectively. The differences are magnified by 20 times. Panels (a) and (c) are |${v}_z$| at receivers 1, 2 and 3. Panels (b) and (d) are |${v}_z$| at receivers 4, 5 and 6.