Sound velocity and related properties of seafloor sediments in the Bering Sea and Chukchi Sea
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Sound velocity and related properties of seafloor sediments in the Bering Sea and Chukchi Sea MENG Xiangmei1, 2*, LI Guanbao1, 2, HAN Guozhong1, 2, KAN Guangming1, 2 1 First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China 2 Key Laboratory of Marine Sedimentology and Environmental Geology, State Oceanic Administration, Qingdao
266061, China Received 10 April 2014; accepted 21 December 2014 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2015
Abstract
The Bering Sea shelf and Chukchi Sea shelf are believed to hold enormous oil and gas reserves which have attracted a lot of geophysical surveys. For the interpretation of acoustic geophysical survey results, sediment sound velocity is one of the main parameters. On seven sediment cores collected from the Bering Sea and Chukchi Sea during the 5th Chinese National Arctic Research Expedition, sound velocity measurements were made at 35, 50, 100, 135, 150, 174, 200, and 250 kHz using eight separate pairs of ultrasonic transducers. The measured sound velocities range from 1 425.1 m/s to 1 606.4 m/s and are dispersive with the degrees of dispersion from 2.2% to 4.0% over a frequency range of 35–250 kHz. After the sound velocity measurements, the measurements of selected geotechnical properties and the Scanning Electron Microscopic observation of microstructure were also made on the sediment cores. The results show that the seafloor sediments are composed of silty sand, sandy silt, coarse silt, clayey silt, sand-silt-clay and silty clay. Aggregate and diatom debris is found in the seafloor sediments. Through comparative analysis of microphotographs and geotechnical properties, it is assumed that the large pore spaces between aggregates and the intraparticulate porosity of diatom debris increase the porosity of the seafloor sediments, and affect other geotechnical properties. The correlation analysis of sound velocity and geotechnical properties shows that the correlation of sound velocity with porosity and wet bulk density is extreme significant, while the correlation of sound velocity with clay content, mean grain size and organic content is not significant. The regression equations between porosity, wet bulk density and sound velocity based on best-fit polynomial are given. Key words: Bering Sea, Chukchi Sea, sound velocity, geotechnical properties, microstructure Citation: Meng Xiangmei, Li Guanbao, Han Guozhong, Kan Guangming. 2015. Sound velocity and related properties of seafloor sediments in the Bering Sea and Chukchi Sea. Acta Oceanologica Sinica, 34(5): 75–80, doi: 10.1007/s13131-015-0669-9
1 Introduction Acoustic properties of seafloor sediments, including sound velocity, have been measured since 1950s in order to (1) constrain inversions of low-frequency geophysical data, especially related to oil and gas exploration, (2) provide geoacoustic models in support of antisubmarine warfare, (3) determine relationships between geotechnical and acoustic properties in support of acoustic surveying techniques, (4) i
