单次与多次散射对地方震尾波的作用

THE EFFECTS OF SINGLE AND MULTIPLE SCATTERING ON CODA WAVES FOR LOCAL EARTHQUAKES

在Aki(1969)的单次反向散射理论和高龙生(1983)的多次散射理论基础上,提出了震源距不为零的单次与多次散射模型。在此模型下,研究了二维无限介质空间中,由统计上均匀分布的各向同性散射体引起的单次与多次散射对地方震尾波功率谱的作用。推导出了二维情况下单次散射和多次散射尾波功率谱的解析表达式,并在二维情况下对不同震源距的单次散射与多次散射对尾波功率谱的作用进行了比较。

Based on the single-backscattering theory of Aki (1969) and the multiple-scattering theory of Gao(1983),a model of single and multiple scattering,with the distance between source and station being not zaro,has been devised in a two dimensional infinite medium. In this model,we considered the effects of single and multiple scattering on coda waves of a heterogeneous medium consisting of uniformly distributed numerous but statistically isotropic scatterers. The power spectral density of coda waves of single and multiple scattering is expressed in analytic form The contributions to the coda power from single and multiple scattering are compared for different distances between the source and station,we obtain the following results: after the direct S-waves,at shorter lapse time,single-scattered waves dominate the earliec parts of the coda,at longer lapse time,the contributions from multiple scattering play an important part in the late parts of the coda waves. And,the longer the distance between source and station,,the earlier the relative time that multiple scattering becomes important.