Scattering of P Waves by Random Heterogeneities with Sizes Comparable to the Wave Length

In order to examine P-wave scattering by random heterogeneities with sizes com-parable to the wave length, ultrasonic model experiments are carried out by using two-dimensional models of media with randomly distributed velocity and density heterogeneities. P waves are observed along profiles transversal to the direction of wave propagation. To examine the attenuation of P wave by the scattering, the (2' value, which is defined as (2-1=2a,/ka where cep and ka are the total scattering coeffici-ent and the wave number of P wave, respectively, is estimated. On the other hand, to examine the fluctuation characteristics of P wave, the QC1 value, which is defined as Qt-1=2ac,,/k „ where ac, is the seismic scattering coefficient defined by Nevsky et al., is estimated. The obtained (2 ' values decrease with the increase of kaa from 4 to 13.5, but the obtained Qt-1 values increase with the increase of kaa from 4 to 13.5, where a is the size of heterogeneity. When k.a=4, (2-1 is more than ten times of Qe-t, but Q-1 and Q1-1 are nearly of the same order when kaa =13.5. This indicates that the order of about 10 ' of the total scattered energy contributes to the fluctuation of the wave field when kaa = 4, but all of the scattered energy contributes to the fluctua-tion when kaa =13.5. 1