摘要
海洋沉积盆地是地球系统中重要的构造单元之一,其形成演化涉及到壳—幔、岩石圈—软流圈以及沉积地层和沉积流体体系等一系列深浅部耦合作用和地球动力学机制的演变。海洋沉积盆地的研究既包括地球深部结构状态、物质组成和构造演化等区域构造方面,也包括盆地内部结构、构造特征以及沉积地层孔隙流体特征等盆地自身构造特征。海底地震仪(Ocean Bottom Seismometer,OBS)广角地震探测,以其深度上穿透能力强和能够同时获取P波和S波速度结构等方面的优势,近年来在海洋沉积盆地区域构造演化、内部结构与构造以及沉积地层孔隙流体发育特征等研究中发挥了越来越重要的作用。在张裂大陆边缘的研究中,OBS广角地震探测所获取的地壳结构模型为划分"火山型"和"非火山型"张裂陆缘提供了直接证据,地壳拉张减薄的程度和空间变化特征为海洋沉积盆地构造演化的动力学模拟提供了约束条件。在盆地内部结构和构造特征方面,OBS深地震探测对盆地内部的盐体构造、岩浆底辟构造等提供了有效成像,并获取了盆地内部超压状态的分布特征,弥补了常规多道地震在探测深度和复杂地质构造背景等方面的缺陷。在海洋沉积盆地内部流体体系的研究方面,OBS深地震探测揭示了天然气水合物储集区的速度结构,进而计算获取了储集区的厚度以及水合物和游离气体在孔隙中的含量。当然,随着OBS地震探测技术的发展、数据处理能力的提高以及仪器设备参数的改善等,未来OBS广角地震探测在海洋沉积盆地动力学演化过程和机制方面的研究中将继续发挥更大更广泛的作用。
Marine sedimentary basin is an important tectonic unit in the earth,and the evolution of marine sedimentary basin involves a series of the coupling and evolution of geodynamic mechanism such as the crust-mantle,the lithosphere-asthenosphere,the strata-fluid deposition. Therefore,the study of marine sedimentary basin dynamics includes deep structure state of earth,material composition and regional tectonic evolution,and also internal structure,tectonic characteristics and pore fluid characteristics strata of the basin. Wide angle Ocean Bottom Seismometer( OBS) seismic exploration is a marine geophysical survey method originated and developed since 1980's and 1990's,which has the advantages of strong penetration capability,high seismic imaging precision and reception of both P-wave and S-wave,and playing an increasing significant role in the research of marine sedimentary basin at the aspect of regional tectonic evolution,internal structure and pore fluid development characteristics of stratain recent years. In the study of passive continental margin,the crustal structure acquired from wide angle OBS seismic data provides the direct evidence that divides the passive continental margins into magma-poor and magma-dominated ones,and the degree of thinning and spatial variation characteristics of crust provide constraints for dynamics simulations of tectonic evolution in marine sedimentary basin. In the study of the structure features of basin,wide angle OBS seismic exploration fills in gaps at the aspect of investigation depth and complex geological structure in conventional multi-channel seismic survey,and acquires overpressure distribution status of basin according to the velocity structure characteristics of strata,and then infer the basin sedimentation velocity and pore fluid characteristics. In the study of internal fluid system in marine sedimentary basin,it reveals the velocity structure of natural gas hydrate reservoir through the analysis and processing of wide angle OBS seismic data,and calculates the thickness of natural gas hydrate reservoir and the content of hydrate and free gas in pore based on the velocity variation. Of course,the future wide angle OBS seismic exploration in the aspect of dynamic evolution and mechanism research in marine sedimentary basin will play a more important role with the development of marine seismic exploration technology,the improvement of data processing and instrument parameters.