南海中南礼乐断裂的海底地震仪探查与研究

南海形成演化的诸多问题是相互纠缠的，牵一发而动全身。“中南—礼乐断裂”的存在性、空间延续性和走向，涉及对东部次海盆与西南次海盆的形成次序和磁异常条带分布及年龄、岩浆活动等方面差异的认识，还涉及南北陆缘的共轭关系及海底扩张机制。因此有必要对其进行探查。本课题拟在前期工作基础上（已在南部和北部陆缘及海盆获取了多条OBS广角地震剖面），用30台左右的海底地震仪（OBS）在“中南-礼乐断裂”的关键部位上横切三条剖面，开展人工震源广角地震探查。重点是：（1）“中南-礼乐断裂”从北到南的走向及变化，特别是其深地壳的连续性；（2）该断裂在西南次海盆的特征，特别是其走向与扩张脊的关系，从而判断断裂的性质（是否是转换断层？）及其对西南次海盆与东部次海盆控制作用；（3）根据该断裂探查结果，研究有关南海形成演化的诸多科学问题。研究方法是射线追踪反演（包括纵波和横波），并结合前期成果进行综合、定量的分析

The vaious questions of the forming and evolution of the South China Sea depend with each other. The questions of the so called “Zhongnana-Liyue Fault” (ZLF)such as its existence,space distribution and orientions are all related with the forming sequence of the eastern sub-basin and the southwestern sub-basin, and their difference in magnetic anomaly direction and age, magma activity and so on. Futhermore, they are related with the conjugate relationship between the northern margin and the southern margin, and the seafloor spreading mechanism of SCS.. Based on our previous researches(several OBS profiles in northern and southern margins), this new proposed project intends to carry out wide-angle OBS seismic experiment of three transecs in the key parts of ZLF by using 30 OBS.The main scientific targets are as follows: (1) The strike direction and its variation of ZLF and its cutting in the deep crust in particular;(2) the characteristics of ZLF in the southwestern sub-basin,especilly the relationship between its strike with spreading ridge, its nature(transformed fault ? or not) and its controlling on the two sub-basins mentioned above;(3) Base on the new results of the experiment in ZLF, then various scientific questions of the evolution of SCS will be discussed. The research methods includs seismic ray-tracing calculation and inversion(P wave and S wave), quantitative analysis and comprehensive research by using previous data and new data.