用小波变换讨论地震中的多普勒现象

地震中多普勒效应可以确定地震的破裂面等，说明对多普勒效应的研究有实际意义，但目前确定地震中是否存在多普勒效应的方法并不成熟。在研究多普勒效应空间分布规律的基础上，提出用小波变换确定地震中是否存在多普勒效应的方法。选择位于汶川地震断层滑动前方的若干台站对台站最初时段的地震记录进行小波变换时，发现随着震中距的增加，小波谱高频幅值明显大于小波谱低频幅值；说明虽然存在介质对地震波的吸收衰减作用，但多普勒效应的存在仍使得小波谱高频幅值增大。选择与汶川地震断层垂直方位的若干台站对台站最初时段的地震记录进行小波变换时，发现随着震中距的增加，小波谱高频幅值迅速降低，震中距大到一定程度后低频部分的小波谱幅值会明显大于高频部分的小波幅值；说明在该方向上，介质对地震波的高频吸收衰减起主要作用，没有发生多普勒效应。

Discussion on Doppler Effect in Earthquakes by Wavelet Transform

The Doppler effect in earthquakes can be used to determine the rupture surfaces of earthquakes,which implies that the study of Doppler effect has practical significance. However, the method to determine whether there is a Doppler effect in earthquakes is not yet mature. On the basis of studying the spatial distribution of Doppler effect, a wavelet transform method is proposed to determine whether a Doppler effect exists in earthquakes. In this study, some stations located in front of the fault slip of Wenchuan earthquake were selected for wavelet transform on the seismic records in the initial period, it was found that with the increase of epicenter distance, the high frequency amplitude of wavelet spectrum was obviously larger than the low frequency amplitude of wavelet spectrum,which indicates that although there was the effect of the media on the absorption and attenuation of seismic waves, the high frequency amplitude of the wavelet spectrum increased due to the existence of a Doppler effect. Several stations located in the vertical direction to the Wenchuan earthquake were selected for wavelet transform on the seismic records in the initial period, it was found that with the increase of epicenter distance, the high frequency amplitude of wavelet spectrum decreased rapidly. When the epicenter distance was large to a certain extent, the amplitude of wavelet spectrum in the low frequency part was obviously larger than that in the high frequency part. In this direction, the medium played a major role in the high frequency absorption and attenuation of seismic wave, and the Doppler effect did not occur.