南海西南次海盆海洋性岩石圈对海底扩张过程响应的综合地球物理研究

The integrated geophysics study of the oceanic lithosphere responses to the course of seafloor spreading of southwestern sub-basin in South China Sea has great significant intellectual merit to the understanding the evolution history, the type of mid-ocean ridge and the global dynamic tectonic background of South China Sea. Based on the multiple channels seismic data, ocean bottom seismometers data and gravimetric data from one deep seismic exploration transect across southwest sub-basin in South China Sea, this proposal carries out systematic research on the relationship between the shallow part structure of lithosphere to the pattern of seafloor spreading. Using the joint inversion technique of wide-angle seismic data, multiple channels seismic data and gravimetric data, the study could unveil the geological structure and physical variation of the lithosphere shallow part. And the course of the seafloor spreading in global tectonic background could be also discussed throughout the study of the morphology of crystallized basement relationship to the oceanic crust thickness and the rate of seafloor spreading. This research intends to provide a comprehensive regional geological and geophysical results interpretation and do a comparative analysis of different seafloor spreading rates effect to the variation properties of oceanic lithosphere structure in order to explore the spreading rate variation pattern during the expansion of South China Sea, which could provide new evidences to deepen the understanding of South China Sea evolution history.

开展南海西南次海盆海洋性岩石圈对海底扩张过程响应的综合地球物理研究对深化认识南海演化历史、南海洋中脊类型以及南海在全球海底扩张下的动力学背景有着重要的意义。本申请以南海深地震探测剖面获得多道地震数据、海底地震仪数据和重力数据为基础，开展针对南海岩石圈浅部结构与海底扩张模式关系的系统研究。通过利用广角地震数据与反射地震、重力数据的联合反演技术，研究岩石圈浅部的地质结构与物质变化；同时通过结晶基底形态与洋壳厚度、海底扩张速率关系的研究，探讨南海在全球海底扩张背景下海底扩张过程。结合区域综合地质地球物理解释结果，对比分析不同海底扩张速率对海洋性岩石圈的构造属性、物质变化的影响，探讨南海海底扩张时期的扩张速率的变化规律，为深化理解南海形成演化历史提供新的地球物理依据。

针对OBS深部地震探测OBS973剖面，建立了不同物理量联合反演方案的优化方案，如反射地震与广角地震数据的联合走时反演，重力与地震数据联合反演及广角地震数据的振幅反演。对深部地震模型构建的过程中，需要增加不同类型地球物理参数及折衷因子，建立了建立地震波走时、振幅和物质密度的联合反演方程，为完成同时利用地震波速度和密度数据进行多参数联合反演成像方法，结合多种地质资料与构造背景，讨论西南次海盆陆缘破裂的过程，随后利用地震资料及重力的约束反演方法讨论了海底扩张期间洋壳的物质分布与变化，分析了残留熔融物质冷却后地对洋壳结构的影响。