Seafloor Sediment Study from South China Sea: Acoustic &amp; Physical Property Relationship

Jingqiang Wang,Tiegang Li,Yongtao Fu,Wenjing Chen,Changsheng Guo,Zhengyu Hou

doi:10.3390/rs70911570

Abstract

Seafloor sediments of different geographical areas in the southern South China Sea (continental shelf, continental slope, and Okinawa Trough) were gravity cored at 21 locations. Sound velocities (V) of the samples were measured at 15-cm increments immediately upon retrieval, and porosity, wet bulk density, and mean grain size were measured later in the laboratory. Empirical equations from previous studies were applied to predict V of sediment samples from the measured physical properties and it was found that the sound velocities derived from the existing equations did not closely match the measured sound velocities. Therefore empirical equations were reconstructed based on the measured data that represent the relationships between physical and acoustic properties of the different geographical area in the study area. Possible explanations for the discrepancies between the measured data and those of previous studies were investigated and found that physical properties, sediment types, geographical area, etc. are important factors that influence sound velocity. The empirical equations of this report should be preferred for prediction of sediment sound velocity for high-frequency acoustic experiments.

Highlights

The acoustic and physical properties of marine sediments in various geographical areas and sedimentary environments are vital to underwater acoustic environment and explorations of the seafloor, and have become an important tool for remote sensing the geophysical properties of the oceans
We present our results and conclusions regarding the relationships of sound velocity to sediment physical properties in different geographical areas, and new empirical equations, which deviate from previously established equations
We conclude the following: (1) Previously established equations relating the physical properties of seafloor sediment to their acoustic properties were not entirely accurate in the study area

Summary

Introduction

The acoustic and physical properties of marine sediments in various geographical areas and sedimentary environments are vital to underwater acoustic environment and explorations of the seafloor, and have become an important tool for remote sensing the geophysical properties of the oceans. Hamilton published numerous papers dealing with the acoustic characteristics of marines sediments from various environments worldwide [5,6,7]. These properties include compressional and shear wave velocities, attenuation, porosity, water content, sand-silt-clay content, wet bulk density, and other physical properties. Hamilton and Bachman [8] used laboratory measurements of sediment properties in cores from the Bering Sea, North Sea, Mediterranean Sea, equatorial Pacific, and other areas to establish empirical equations for sound velocity in seafloor sediments. Orsi and Dunn [9] showed a correlation between sound velocity and physical properties of fine-grained abyssal sediments from the Brazil Basin

Methods

Results

Conclusion