地震波是一种非平稳信号，传统的傅里叶变换已不适用，时频分析方法能在时间—频率域给出非平稳信号不同时刻的频率分布特征。Wigner-Ville分布（WVD）对非平稳信号具有较好的时频聚集性，但因其为双线性变换，会产生严重的交叉干扰项。短时傅里叶变换（STFT）是一种线性变换，不存在交叉项干扰，但时频聚集性较差。考虑到二者优点，在对地震波进行时频分析时，采用短时傅里叶变换和Wigner-Ville分布的联合算法，既有效抑制了Wigner-Ville分布交叉项干扰，又保持了较高的时频聚集性。通过3种方法，对模拟信号和实际数据处理结果进行对比分析，发现联合算法对获取地震波信号的时频特征和纵波到时检测，具有更好效果。%Seismic signal is a kind of non-stable signal,which can’t be analyzed suitably by classical Fourier analysis. Time-frequency analysis can analyze non-stationary signal in time-frequency domain and show out the distribution characteristics. WVD has perfect time-frequency concentration,but because it is a bilinear transformation,the existence of cross-terms is inevitable. STFT is linear transformation,has no cross-terms,but affected by the window size, it has bad time-frequency concentration. Based on the advantage of these two methods,we propose to obtain the time-frequency distribution by the combined method. This method can suppress the cross-term interference in WVD effectively,while keeping the excellent time-frequency concentration. By calculating simulation signal and actual data,the comparison result of STFT,WVD and the combined method indicates that the combination method is most suitable for computing the time-frequency distribution characteristics of earthquake waveform signal and more effective to detect the arrive time of P-waves.
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