2次元ランダム媒質モデルにおけるP波の散乱減衰特性について

Abstract

In order to examine the attenuation property of P waves by the scattering due to randomheterogeneities, ultrasonic model experiments are carried out by using two-dimensional modelsof media with randomly distributed velocity and density heterogeneities. The main experimentalresults are as follows. (1) P-wave attenuation by the scattering is negligible in the low-frequencyrange (22ra/h<<1) where the wave length h is much longer than the size a of heterogeneity, and isespecially remarkable in the intermediate frequency range (about 1<2ra/h<4) where h is compara-ble to or longer than a, and shows a decreasing behavior with the decrease of h(4<2ra/h<10), andis not found in the high-frequency range (2ra/h>>10) where h is shorter than a. (2) When thepredominant wave length of incident P waves is two to three times the size of heterogeneity(2<22ra/h<3), the predominant frequency of transmitted P waves becomes higher with theincrease of travel distance.