Characteristics of Acoustic Wave Reflection From the Transition Layer

of Surficial Marine Sediment

A0065 Masao Kimura Tokai University

A0066 Takuya Tsurumi Tokai University

It has been recently reported that the porosity and the density etc.

in the surficial marine sediment vary largely with the depth. The

characterisitics of acoustic wave reflection from such transition

layer of the surficial marine sediment seem to be very different from

that from uniform sediments. In this study, the incident angle

dependence of the reflection coefficient for the transition layer of

the surficial marine sediment model is calculated using OASES (Biot-

Stoll model). The effects of the transition layer, and the frequency

dependence of the reflection coefficient characteristics are

investigated. Next, the characteristics of the incident angle for the

reflection coefficient are measured in water tank and in situ. Beach

sand (fine sand) are used for water tank measurements, and in situ

measurements are done in a very fine sand bottom The operating

frequency is 150 kHz. The incident angle are 0, 20, 50, and 60

degrees. The measured results are compared with the calculated

results using OASES Biot-Stoll model), and the effects of the

trasition layer on the characteristics of the reflection coeffieint

are investigated.