Comprehensive study of scattering,intrinsic and coda attenuation in the Yunnan area

The scattering and the intrinsic attenuations below stations in the Yunnan area are obtained by using the earthquake waveform data recorded through the remote digital seismic network of the Earthquake Administration of Yunnan Province,and by adopting the multiple lapse time window analysis method.The code attenuation of different stations is obtained through the single scattering model.The study result shows that,as for the spatial distribution of scattering attenuation,intrinsic attenuation,total attenuation and code attenuation,the Jinshajiang-Honghe fault serves as the border between low attenuation in the western area and high attenuation in the eastern area.The earthquake wave attenuation in the Yunnan area is mainly intrinsic,since the intrinsic attenuation Q_i~(-1) of all stations is larger than the scattering attenuation Q_s~(-1) on three respective frequency bands of 2～4 Hz,4～8 Hz and 8～16 Hz, while on the frequency band of 1～2 Hz,the intrinsic attenuation of individual stations is obviously smaller than the scattering attenuation but the intrinsic attenuation of most stations is larger than or equal to the scattering attenuation Q_s~(-1).The code attenuationQ_c~(-1),on the frequency band of 1～2 Hz,is slightly larger than the intrinsic attenuation but smaller than the total attenuation,while the code attenuationQ_c~(-1),on the frequency band of 2～4 Hz,4～8 Hz and 8～16 Hz,is close to the total attenuation and,at individual stations,is larger than the total attenuation.The relationship between the scattering attenuation and the frequency in the Yunan area can be expressed as Q_s~(-1) = 0.0138f~(-1.61);for the intrinsic attenuation and the frequency,it isQ_i~(-1) = 0.0119 f~(-0.86);and for the total attenuation and the frequency,it is Q_t~(-1) = 0.0247 f~(-1.1);for the code attenuation and the frequency,it is Q_c~(-1)= 0.0129f~(-0.71). Compared with other areas worldwide,the scattering attenuation in the Yunan area is of a lower middle level and the intrinsic attenuation is of an upper middle level.