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 Q c −1 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 Q s −1 and intrinsic attenuation Q i −1 were separated from total attenuation Q t −1 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 Q i −1 is comparable with Q s −1 at 1–2 Hz, and after 1–2 Hz, Q i −1 is greater than Q s −1 and dominates the attenuation process. Q c −1 is close to Q i −1 at other frequency bands except 1–2 Hz. Results show that Q −1 especially Q s −1 varies spatially, Q −1 in eastern Yunnan zone is a bit higher than in north-western Yunnan zone; northwestern Yunnan zone higher than southwestern Yunnan zone. Comparing with other results in global, Q s −1 in Yunnan is lower than the global average value among these results, Q i −1 is higher than the global average value, and Q t −1 lies the middle among these results.