U. S.-Korea Cooperative Research on Acoustic Properties of Fine-Grained Gas-Bearing Sediments Offshore SE Korea

9816277wilkens该奖项将资助夏威夷大学夏威夷地球物理研究所的Roy H. Wilkens博士与韩国忠南国立大学海洋学系的Soo-Chul Park博士进行为期24个月的关于朝鲜半岛东南海岸细粒含气沉积物声学特性的合作研究。海底沉积物中气泡引起的声浊现象在世界范围内普遍存在，但目前对其了解甚少。即使沉积物中微小的气体痕迹没有表现出声浊度，也会使纵波速度减慢到影响双向地震传播时间到深度的转换的程度。在沉积物-海水体系中，海床上10米处的物理和声学特性梯度最大。在这个区域内，孔隙度可能变化20-30%(1.0 - 0.7)，密度可能变化50% （1.02-1.50 gm/cc）。纵波速度通常变化很小，保持与水的速度接近，因此声阻抗的变化和反射器的位置是由这10米层内密度剖面的变化决定的。这个一般规则的一个例外是当气体存在于沉积物孔隙流体中时。PI对波罗的海含气沉积物中的声速进行了测量，而他的韩国合作者正在朝鲜半岛东南沿海进行此类研究。目前的合同将允许PI访问韩国，共同规划和随后的合作研究，乘坐韩国的研究船，详细调查这个接近海底的气体沉积物带上面和里面的各种特性的行为。两个研究小组的测量技术的结合和专业知识的融合有望使双方的科学项目受益匪浅。该项目与美韩合作科学项目的目标相关，该项目旨在通过科学信息、思想、技能和技术的交流以及在互利问题上的合作，提高美韩科学家和工程师之间的合作水平。韩国的参与得到了韩国科学与工程基金会（KOSEF）的支持

9816277WilkensThis award provides funds to permit Dr. Roy H. Wilkens, Hawaii Institute of Geophysics, University of Hawaii, to pursue with Dr. Soo-Chul Park, Department of Oceanography, Chungnam National University, Korea, for 24 months, a program of cooperative research on acoustic properties of fine-grained gas-bearing sediments off the southeast coast of the Korean peninsula. Acoustic turbidity caused by gas bubbles in seafloor sediments is a common occurrence worldwide, but it is as yet poorly understood. Even minute traces of gas in sediments that do not exhibit acoustic turbidity can slow compressional wave velocity to such an extent as to influence the conversion of two-way seismic travel time to depth.The upper 10 meters of the seafloor contain the largest gradients in physical and acoustic properties in the sediment-seawater system. Within this zone porosity may change by 20-30% (1.0 to 0.7) and density may vary by 50% (1.02-1.50 gm/cc). Compressional wave velocities usually change very little, remaining close to that of water, so that acoustic impedance changes and reflector positions are dictated by inflections in the density profile within this 10 meter layer. One exception to this general rule is when gas is present in sediment pore fluids. The PI has made measurements on the velocity of sound in gas-bearing sediment in the Baltic Sea, while his Korean collaborator is conducting such studies along the southeast coast of the Korean Peninsula. The present award will allow the PI to visit Korea for joint planning and subsequent cooperative research, aboard Korean research vessels, to investigate in great detail the behavior of various properties above and within this near seafloor gassy sediment zone. The scientific programs of both collaborators are expected to benefit greatly from the combination of measuring techniques and blending of expertise of the two research groups. This project is relevant to the objectives of the U.S.-Korea Cooperative Science Program which seeks to increase the level of cooperation between U.S. and Korean scientists and engineers through the exchange of scientific information, ideas, skills, and techniques and through collaboration on problems of mutual benefit. Korean participation is supported by the Korea Science and Engineering Foundation (KOSEF).***