Geoacoustic model based on physical property characterization of Quaternary sediments off eastern Geoje Island, Korea Strait

Drilled-core samples (21ESDP-205, 21ESDP-206) collected from off eastern Geoje Island (Korea Strait) were used to characterize physical properties of the area with respect to sedimentary depth. Laboratory analyses of the acoustic and physical properties of the samples were conducted and shear-wave velocity, velocity ratio, poisson’s ratio, and velocity anisotropy were calculated. In particular, lithological characteristics of two drilled-core samples were interpreted using both visual description and geoacoustic and physical property data. In addition to visual description, a relationship between mean grain size and dry bulk density was used to interpret lithological characteristics. In other word, the values greater than approximately 1 g/cm³ in dry bulk density may be corresponded toward coarse grained sediments, except for the relationship caused by compaction effect. As a result, geoacoustic and physical property data at the two sites were in correlation with lithological characteristics alternating (mainly between sandy mud and muddy sand) at sedimentary depth. The relationships between velocity and porosity showed better correlation than those of between velocity and wet bulk density. Geoacoustic units (GAUs) identified from sites 21ESDP-205 and 21ESDP-206 were divided into 12 and 14 units with sedimentary depth, respectively, and geoacoustic models were developed for the sedimentary layers around these sites. The upper sediments in the study area were largely originated and redistributed from the Nakdong River, caused by sea-level changes during the Quaternary. These results suggest that sedimentary physical properties in the region were primarily controlled by depositional processes linked to the river, and that sea-level changes played a significant role as a dominant sedimentary process during the Quaternary.