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

9816277Wilkens该奖项提供资金，允许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Park Soo-chul博士进行为期24个月的关于朝鲜半岛东南海岸细颗粒含气沉积物声学性质的合作研究计划。海底沉积物中气泡引起的声学浑浊是世界范围内的常见现象，但人们对其了解甚少。即使是在沉积物中不表现出声波浑浊的微量气体也会使纵波速度变慢，从而影响双向地震走时到深度的转换。在沉积物-海水系统中，海底上部10米处包含最大的物理和声学性质梯度。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克/毫升)。纵波速度通常变化很小，保持在接近水的位置，因此声阻抗的变化和反射层的位置由这10米层内密度剖面的反转决定。这一一般规律的一个例外是当沉积物孔隙流体中存在气体时。少年派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的东南海岸进行这样的研究。本合同将允许国际和平研究所访问韩国，在韩国考察船上进行联合规划和随后的合作研究，以更详细地调查这一近海底含气体沉淀区上方和内部的各种财产的行为。预计两位合作者的科学计划将从两个研究小组的测量技术和专业知识的结合中受益匪浅。该项目与美韩合作科学计划的目标相关，该计划旨在通过交流科学信息、想法、技能和技术以及通过在互利问题上的合作来提高美国和韩国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).***