Characteristics of coda wave attenuation in Yunnan area

Abstract

The characteristic of seismic coda wave attenuation in Yunnan area in 7 frequency-bands range from 1 Hz to 20 Hz was estimated by using the local earthquake′s waveform data recorded from 22 Yunnan digital seismic stations. Coda attenuation 1 c − Q of each station was firstly calculated by single scattering method. Then, mean free path L e and seismic albedo B 0 of each station were calculated, and scattering attenuation 1 s − Q and intrinsic attenuation 1 i − Q were separated from total attenuation 1 t − Q by multiple lapse time window analysis based on the multiple scattering model in uniform random isotropic scattering medium. The attenuating characteristics in Yunnan show that most value of L e are in 10~30 km, with maximal within 2~6 Hz; B 0 are about 0.5 at 1~2 Hz, but less than 0.5 at other frequency-bands, which means 1 i − Q is comparable with 1 s − Q at 1~2 Hz, and after 1~2 Hz, 1 i − Q is greater than 1 s − Q and dominates the attenuation process. 1 c − Q is close to 1 i − Q at other frequency bands except 1~2 Hz. Results show that Q −1 especially 1 s − Q varies spatially, Q −1 in eastern Yunnan zone is a bit higher than in northwestern Yunnan zone; northwestern Yunnan zone higher than southwestern Yunnan zone. Comparing with other results in global, 1 s − Q in Yunnan is lower than the global average value among these results, 1 i − Q is higher than the global average value, and 1 t − Q lies the middle among these results.