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Abstract

The in-situ velocity of unconsolidated shelf sediments in the western South Korea Plateau of the East Sea was directly measured using the Korea Institute of Geoscience and Mineral Resources (KIGAM) Seafloor Acoustic Probe. Physical properties, including laboratory velocity, were also measured for core samples collected from the same location. The laboratory measurements were conducted at a temperature of 23℃ and under atmospheric pressure. Owing to the in-situ temperature and pressure (0.5–1.5℃ and 100–180 atm, respectively) at the sampling site, the laboratory velocity was adjusted to the in-situ conditions. In addition, a comparison with a theoretical prediction model (Biot-Stoll model) was performed. The in-situ velocity measured by KISAP ranged from 1425 to 1475 m/s in muddy sediments. The laboratory velocities obtained from the core samples were slightly higher than the in-situ velocity in the range of 1500–1570 m/s. The velocity difference between the in-situ and laboratory measurements was approximately 75 m/s. In general, the in-situ velocities substantially differ from laboratory velocities owing to differences in temperature, pressure, and measurement methods. As a rule, the difference increased with grain size. Nevertheless, the corrected laboratory velocities correspond well with the KISAP data, except for the intervals where the coarse-grained particles (such as tephra) are composed of thin layers. The measured in-situ and laboratory velocities, corrected into standard conditions, were mostly within the range of curves predicted by B-S model.

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