Laboratory/In situ Sound Velocities of Shelf Sediments in the South Sea of Korea

Geoacoustic Estimation of the Seafloor Sound Speed Profile in Deep Passive Margin Setting Using Standard Multichannel Seismic Data

“…The sound speed in the seafloor marine sediments can be estimated through several approaches: (1) direct methods [10][11][12], (2) empirical relations [10,13] and/or physical models [14][15][16][17], (3) in situ acoustic measurements [2,[18][19][20] and (4) remote sensing using acoustic and seismic methods.…”

“…For instance, Hamilton and Bachman [10] used a pulse transmission technique at a frequency of about 200 kHz to measure the sound speed in the cores; the estimated margins of error were ±3 m s −1 for clays and ±5 m s −1 for sands. Kim et al [12] conducted laboratory measurements of compressional sound speeds of shelf sediments (~50 m bottom depth) in the South Sea of Korea for six 1-3.5 mlong cores using an automated sound-speed-measurement technique with a 1 MHz PZT transducer [21]. It was modified from the pulse transmission technique [11] and provided sound-speed accuracy of approximately 1%.…”

“…It was modified from the pulse transmission technique [11] and provided sound-speed accuracy of approximately 1%. However, the estimation of in situ sound speed from laboratory measurements is challenging due to: (1) the disturbance of the sediment cores during their extraction from the sediment, which introduces bias into the laboratory measurements; and (2) different scales and environmental conditions between the laboratory and the seafloor (i.e., pressure, temperature, measurement frequency) [12].…”

“…The uncertainty of such measurements may be high relative to the laboratory measurements. For instance, the uncertainty of the SAMS was from ±8.7 up to ±24.8 m s −1 depending on the position and frequency used [20], which is higher than the uncertainty of laboratory measurements reported by Hamilton and Bachman [10] and Kim et al [12]. In addition, direct acoustic methods, both in the laboratory and in situ, require immense efforts and become expensive when large areas are investigated, especially in spatially and temporally heterogeneous regions [7,22].…”

“…These results are in good agreement with our results, considering the silty-clay composition of the seafloor in the study area. Kim et al [12] estimated, in the laboratory, the sound speed of silty-clay sediments from six 1-3.5 m-long cores, which were obtained from the South Sea of Korea (~50 m bottom depth) using the pulse transmission technique (frequency of 1MHz). They reported sound-speed estimates ranging from 1503 to 1604 m s −1 , and the measurement accuracy was approximately 1%.…”