Wavelet power spectrum analysis of the electromagnetic signals of Wenchuan M_S8.0 and Haiti M_W7.0 earthquakes

Wavelet transform technique is applied to the analysis of geo-resistivity data observed at Chengdu and Jiangyou stations before and after Wenchuan M_S8.0 earthquake in 2008 and the ionospheric magnetic field recorded by DEMETER satellite before and after the Wenchuan earthquake and the 2010 Haiti earthquake, in order to study the wavelet power spectrum of geo-resistivity and ionospheric magnetic field and its relative variation. Our analysis result suggests that ① the wavelet power spectrum and its relative variation increased greatly at the times when the geo-resistivity of N58°E channel of Chengdu station displayed its medium-term decrease and short-term increase, the impending anomaly was recorded on the N10°E channel of Jiangyou geo-resistivity station and the wavelet power spectrum of x component of ionospheric magnetic field and its relative value increased distinctly before Wenchuan earthquake, showing typical Earth-space electromagnetic anomaly of geo-resistivity and ionospheric magnetic field; ② The wavelet power spectrum of x and z components of ionospheric magnetic field and its relative variation also increased greatly before Haiti earthquake, similar to the increase before and after Wenchuan earthquake.