散乱による地震波コーダ生成モデルの模型実験による検定

Abstract

We produced seismograms with long codas using ultrasonic technique and 2-D modelmedia with scattering coefficient g of 0.008 to 0.13 km 1. The amplitude decay of the codawas analyzed up to lapse time t=350 microsec (corresponding to 35 sec in seismic coda).From a comparison of the coda decay among seismograms produced by our experimentsand those predicted by single- and multiple-scattering models, the following results wereobtained: (1) There is no discrepancy between the coda decay observed by using model mediawith g<0.024 km 1 and that predicted by Gao et al.'s model for t<35 sec. (2) The lapsetime t, at which we find a discrepancy between the coda decay observed in the experimentsand that predicted by the single-scattering model, nearly agrees with critical travel time tcby Gao et al. (3) In the Kinki district, when quality factor due to absorption, Qab, is assumedto be 1000, the critical time tc for 2-Hz and 16-Hz waves is 11 and 6 sec, respectively.