Abstract: Using the Sato's single isotropic scattering model, the authors calculated the S-coda attenuation factor Q_c values of 1999 Xiuyan M_L5.9 earthquake sequence at Xiuyan station and Yingkou station. And the temporal changes of Q_c in three components and 10 center frequencies are obtained for the two stations. Dividing the sequence into three time periods by the occurrence of two main quakes, the Q_c and frequency relation for the three time periods and total time sequence were calculated. The results show that Q_c increases in trend before the strong earthquake and decreases after the strong earthquake. The changes of Q_c vary at different stations and in different components. Compared it with Aki's single backscattering model, the authors believe that Sato's model is more reasonable for our data processing.

Key words: S-Coda attenuation factor Q_c, Xiuyan earthquake sequence, Sato single isotropic scattering model, Aki single backscattering model