Imaging Fine-scale Density Structure in the Ocean with Seismic Reflection Data

利用地震反射数据对海洋中的精细密度结构进行成像

• 批准号: 0526632
• 负责人: Anne Tréhu
• 金额: --
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-01 至 2009-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0526632&HistoricalAwards=false
• 关键词: Imaging; Fine; scale; Density; Structure

Recent studies have shown that boundaries between water masses of different density result in reflections that can be observed in seismic data originally acquired to image the structure beneath the seafloor. Because seismic reflection data have been collected throughout the world oceans over past several decades, they provide an opportunity to extend spatial and temporal constraints on a variety of ocean processes. It is proposed to examine the extensive seismic reflection database collected since the mid-1980s along the continental margin of the western US, which were originally acquired to study tectonic processes associated with the Mendocino transform fault and Cascadia subduction zone. One objective is to analyze local perturbations of the density field that are observed over the eastern end of the Mendocino Escarpment to test the hypothesis that they result from tidally induced mixing. A possible reflection from the top of a bottom mixed layer may also be associated with interaction of internal waves with the seafloor on the flank of the Escarpment. Another objective is to determine temporal and spatial variations in the strength and distribution of eddies in the California undercurrent. These eddies have been detected by drifters and are apparent in the extensive hydrographic data base acquired offshore Oregon and northern California between 1997 and 2003 as part of the NSF/NOAA GLOBEC program. Because the hydrographic and seismic data overlap in time and space, there is an opportunity to test the validity of ocean density models derived from seismic data and map the spatial extent of the eddies a times in the past when no other data to do this exist, thus extending the historical record. Reprocessing and inversion will be needed to optimize imaging of the fine-scale velocity/density structure of the ocean; most of the existing data have been processed using parameters that have distorted, and often eliminated, signals originating in the ocean rather than beneath the seafloor. Changes in ocean current regimes have broad impacts on ecology and climate. The project will also provide training for a graduate student in digital signal processing techniques of broad applicability in geophysics. Finally, the results will be used in public presentations that the PIs give in local schools and other forums designed to transmit the importance and excitement of earth science and oceanography.

最近的研究表明，不同密度的水体之间的边界会产生反射，这些反射可以在最初获取的地震数据中观察到，这些数据是为了对海底结构进行成像。由于地震反射数据是在过去几十年中收集到的，因此它们为扩展各种海洋过程的时空限制提供了机会。本文建议对20世纪80年代中期以来沿美国西部大陆边缘收集的大量地震反射数据库进行研究，这些数据库最初是为了研究与门多西诺转换断层和卡斯卡迪亚俯冲带相关的构造过程而获得的。其中一个目标是分析在门多西诺悬崖东端观测到的密度场局部扰动，以检验它们是由潮汐引起的混合造成的假设。来自底部混合层顶部的可能反射也可能与内波与悬崖侧面海底的相互作用有关。另一个目标是确定加利福尼亚暗流中漩涡强度和分布的时空变化。这些涡流已被漂流者探测到，并在1997年至2003年期间作为美国国家科学基金会/美国国家海洋和大气管理局GLOBEC项目的一部分在俄勒冈州和加利福尼亚北部近海获得的广泛的水文数据库中很明显。由于水文和地震数据在时间和空间上重叠，因此有机会测试由地震数据导出的海洋密度模型的有效性，并在没有其他数据存在的情况下绘制过去一次涡流的空间范围，从而扩展历史记录。为了优化精细尺度海洋速度/密度结构的成像，需要进行后处理和反演；大多数现有的数据都是用参数处理的，这些参数扭曲了来自海洋而不是海底的信号，往往还会消除这些信号。洋流状态的变化对生态和气候有着广泛的影响。该项目还将为一名研究生提供在地球物理学中广泛适用的数字信号处理技术方面的培训。最后，研究结果将用于pi在当地学校和其他论坛上的公开演讲，旨在传递地球科学和海洋学的重要性和兴奋。