Precursory or atmospheric waves?Comments on“Analysis of characteristics of precursor wave of low frequent in Shanxi before Wenchuan M_S8.0 earthquake” by Zhang et al (2009)

On May 11 2008, some“precursory waves”were obviously recorded at five stations in Shanxi Province, but their real physical nature is still under debate. To uncover these important phenomena, we adopt the wavelet transform method to diagnose the correlations between atmospheric and precursory waves at different frequency bands. Furthermore, we compare the typical variations induced by the fluctuations of atmospheric pressure to the “precursory waves”aiming to analyze the similarities between them. The results show that the physical origin of these “precursory waves”mainly comes from the atmospheric waves rather than from the Wenchuan M_S8.0 earthquake.