Two sorts of echoes caused by the reradiation of elastic surface wave have been observed in experimentation: the radial surface backscatteringwave and the longitudinal surface backscatteringwave.
实验观测到两类由弹性表面波的再辐射产生的回波：径向表面反向散射波和纵向表面反向散射波。
2
This kind of methods is also called as undulation forecast subtracting, which including wave field extrapolated method, feedback loop method and backscattering progression method.