用海底地震仪（OBS）被动源记录反演洋中脊岩石圈结构

大洋中脊和边缘海扩张脊的深部构造是研究海底扩张和洋壳形成动力学机制的关键。重力和面波方法精度和分辨率较低并存在多解性，人工源OBS探测深度不够，导致对一些关键部位（活动喷口或熔融地幔）的深部结构和动力学过程缺乏证据，因为很难获得这些关键点的莫霍面反射震相PmP，而且P波速度对热力学状态不敏感。本申请拟利用在超慢速西南印度洋中脊、南海海盆残留扩张脊、南北极部分海域获得的宽频带OBS天然地震记录，采用接收函数方法，反演洋中脊/扩张脊深部地壳和岩石圈精细结构。目标是突破OBS被动源接收函数反演的技术瓶颈；获取超慢速西南印度洋中脊、南海残留扩张脊和南北极部分海域的岩石圈S波速度结构；对洋中脊动力学和岩浆活动深部热力学机制提出新的认识。拟解决的关键问题是，用实测数据给出洋中脊特别是活动喷口下方对熔融状态敏感的S波速度结构。 创新点：调研表明用OBS的被动源数据开展接收函数反演，在国内外都是首创。

The deep structures of oceanic or marginal sea ridges play an important role in understanding the mechanisms of seafloor spreading and crust formation. However, the results derived from gravity or seismic surface wave data have low resolution together with multiple solutions, and the active OBS experiment is limited in exploration depth resulting in the absent of proofs for deep structure and dynamic process at some key special ridge portions such as hydrothermal vents or melting mantle. The main problem is due to the absent of Moho reflection signal PmP and the low sensitivity of P wave velocity to thermal dynamics. This new proposed object intends to use receive function for inversion high resolution 1D structures at ultra-slow spreading Southwest Indian Ridge, residual ridge of the South China Sea and the basin area of the Poles based on OBS observed passive seismic data. The project scientific targets include three aspects: (1) Establishing a reliable approach of OBS passive seismic receive function that is a problem has not been solved yet; (2) Modeling the shear wave velocity lithosphere structures at SWIR, SCS and the polar areas; (3) Improving the understanding of ridges dynamics and magma activity deep thermal mechanism..The key of this project is to use observed data to derive high resolution S-wave velocity models that are sensitive to mantle melting, especially the structures beneath ridge active vents. This project is characterized by its first research in the world using OBS passive seismic receive function method to inverse lithospheric structures.