Geoacoustic provinces of the South Sea shelf off Korea

In order to characterize geoacoustic provinces of the South Sea shelf of Korea, sediment texture, physical, and geoacoustic properties (p-wave velocity) were measured and calculated based on approximately 350 core samples collected from the study area. The empirical relationship between mean grain size and velocity suggested by Hamilton was used for calculation of p-wave velocity. The inner shelf sediments of the South Sea are characterized by Holocene muddy sediments derived from nearby rivers (i.e., mostly supplied from Nakdong and Seomjin rivers near the Korean shore), whereas the outer shelf areas are dominated by Quaternary sediments (e.g., relict sediments, due to a rising of sea level during the Quaternary) depending on seafloor bathymetry. In this study, the seafloor of the South Sea shelf is differentiated into 4 provinces based on sediment properties (esp. mean grain size and velocity). Province I consisted of muddy sediments affected directly by the Nakdong and Seomjin Rivers discharge. Province II was covered by the sediments transported from two rivers. Province III is marked by mixed Holocene fine materials and coarse Pleistocene materials. Province IV is dominated by relict sediments characterized by Pleistocene coarse sandy materials. Mean grain size, velocity, and wet bulk density increase from Province I (>7.4 phi,1515 m/s, and 1.52 g/cm(3), respectively) through Province II (5.4 phi, 1597 m/s, and 1.69 g/cm(3)) to Province Ill (2.9 phi, 1766 m/s, and 2.0 g/cm(3)). Porosity, on the other hand, exhibits an opposite trend, decreasing from Province 1(71.3%) to Province 11 (60.3%) and decreasing significantly in Province III (44.6%). Province IV is characterized by the highest velocity (1979 m/s average) and the coarsest material (2.1 phi). Nevertheless the values of physical properties such as wet bulk density, porosity, and density lie between Province II and III. (C) 2012 Elsevier Ltd and INQUA. All rights reserved.