中文说明：S变换时Stockwell提出的一种时频分析方法，主要用于对波场数据进行时频分析。计算得到的幅值是该波的能量大小，计算出来的速度是波传播时的群速度，而非相速度。
English Description：
S-transform is a time-frequency analysis method proposed by Stockwell, which is mainly used for time-frequency analysis of wave field data. The calculated amplitude is the energy of the wave, and the calculated velocity is the group velocity, not the phase velocity.