西太平洋边缘海微地动噪音机理研究

微地动是在全球的地震台站上都能观测到的背景地震噪音，它反映的实际上是大气-海洋-固体地球三圈耦合。微地动仍有不少未解的问题。传统观点认为单频微地动只能在浅海产生，但我们近期及其它个别研究在深海也观测到了单频微地动。这些观测到底是因海底观测能力加强而发现的真实存在还是因数据处理流程不当产生的假象仍然存疑。如果深海的确观测到了单频微地动，将彻底颠覆现有对单频微地动激发机理的认识。此外，双频微地动分裂存在时空变化，但造成这种变化的原因却不甚清晰。最后，现有研究多聚焦于大洋，对边缘海的研究很少。本项目计划利用日本DONET和S-net海底观测网数据，结合同济大学在南海已经回收的海底地震仪数据以及正在实施的海底观测大科学工程数据，并结合陆上地震数据和海洋气象资料，来对比菲律宾海、西太平洋、南海和东海的微地动特征，尝试填补西太边缘海微地动研究的空白，并解答上述微地动领域的全球问题。

Microseisms is a background seismic noise generated by the interaction of the Earth's hydrosphere and lithosphere. It can be observed at seismic stations all over the world. In fact, due to the influence of the atmosphere on the hydrosphere, microseisms actually reflects the atmosphere-ocean-lithosphere coupling of the Earth. Although there has been an increasing interest on microseisms in recent years, there are still many unsolved questions, such as whether the single-frequency microseisms can occur in the deep sea or not? what's the splitting mechanism of double-frequency microseisms? The characteristics of microseisms vary with regions, and among those characteristics which is global and which is local? Especially for single-frequency microseisms, the traditional view is that it can only be generated in shallow water, but our recent research and a few studies by others have oberved single-frequency microseisms in deep sea. It is worth to examine whether these observations are real or artifacts due to improper data processing. If single-frequency microseisms are observed in the deep sea, it will completely overturn the existing understanding of the mechanism of single-frequency microseisms. Moreover, most of the existing studies focus on the open oceans, and few on marginal seas. This project plans to use seismic data collected on the seafloor near the Nankai trench by the DONET (Dense Ocean-floor Network System for Earthquakes and Tsunamis) and S-net in Japan,seismic data collected in the South China Sea by Tongji university and data to be collected by China National Scientific Seafloor Observatory under implementation in the East China Sea by Tongji University, and combined with seismic stations inland or on islands as well as ocean and climate data to study the characteristics of microseisms in the Phillipine Sea, western Pacific, South China Sea, and East China Sea. We will investigate the questions related with the source depths of single-frequency microseisms and the split of double-frequency microseisms, combined with the seabed topography and sediment thickness in the marginal seas. This project will not only fill up the gaps of studies on microseisms in the marginal seas of western Pacific, but also contribute to the above global questions on microseisms.