南海东北部陆坡与恒春海脊天然气水合物分布的地震反射特征对比

对“探宝号”调查船2001年8月在南海东北部陆坡及台湾南部恒春海脊海域采集的多道地震剖面资料进行了地震反射波数据分析、解释和研究,并对南海北部陆坡、陆隆及其东侧俯冲带等区域天然气水合物矿藏的成藏规律及分布特征作了初步的分析与探讨,结果表明:(1)南海东北部陆坡和台湾南部恒春海脊海域地震剖面上均显示有BSR,但两区域构造成因、形式和相关地质环境的不同造成了天然气水合物的成因及过程不同。(2)南海东北部陆坡区域的天然气水合物形成与该区广泛发育的断裂带、滑塌构造体及其所形成的压力场屏蔽环境有关,而台湾南部恒春海脊海域天然气水合物的形成则与马尼拉海沟俯冲带相关的逆冲推覆构造、增生楔及其所对应的海底流体疏导体系有关。(3)南海陆缘区域广泛发育有各种断裂带、滑塌构造体、泥底辟、俯冲带、增生楔等,且温压环境合适,是天然气水合物矿藏极有可能广泛分布的区域。

A study on the seismic reflection of the gas hydrate distribution at the northeast SCS slope and Hengchun ridge

By analyzing and interpreting the newly acquired seismic profile supported by national 973 investigation projects and synthesizing the data with the other related geologic and geographic information,we support the argument that the reflections located at the northeast SCS slope and Hengchun ridge are the Bottom Simulated Reflection(BSR) as shown on the seismic profile.The genesis of the gas hydrate in these two areas is different because of the different regional tectonics and geologic environment.The gas hydrate located at the northeast SCS slope is related to the broadly existed fracture zone,slumping accretion and the distinctive environment of pressure masking field caused by them.But the genesis of the gas hydrate at the Hengchun ridge is associated with the thrust nappe structured accretionary wedges formed along Manila subduction zone and the related sea-floor fluid channel system constructed by them and other faults.Since the analogous geologic bodies are broadly distributed at the SCS and the temperature-pressure environment is very suitable for the formation and deposition of the gas hydrate,we suggest that much more of this resource should be stored in this area.