南海北部珠江口盆地海底蠕变区的形成机理及不稳定性研究

Submarine creep is the prelude and indication of the destabilization of submarine slopes, and it can evolve into large-scale submarine landslides. It is one of the deep-water geohazards that pose the greatest threat to marine engineering structures and human life. However, the formation mechanism and instability of the submarine creep zone are still not fully revealed. This project chooses a submarine creep zone on the southeastern continental slope in the Pearl River Mouth Basin of northern South China Sea as the research area. Through a combination of geophysical data interpretation, sediment sample analysis and numerical simulation, this project attempts to reveal the formation mechanism of the submarine creep zone and analyze its instability quantitatively. Firstly, the internal geological structure of the submarine creep zone will be obtained by seafloor topography analysis and 3D seismic interpretation, and the initial geological model can be established. Secondly, sediment samples will be tested and analyzed in order to provide the constraints for the numerical simulation of the formation processes of the submarine creep zone. Finally, we will simulate the deformation processes of shallow strata in the submarine creep zone and calculate the instability coefficient in order to reveal the formation mechanism of the submarine creep zone and the effect of different controlling factors on the creep processes of shallow strata. Our work will not only promote the research on the formation mechanism of submarine creeps and landslides theoretically, but also be beneficial to the assessment of deep-water geohazards on the continental slope of northern South China Sea.

海底蠕变是海底陆坡地层倾于发生破坏的前奏和指示，能够演变为大规模的海底滑坡，是对海洋工程结构及人类生命安全威胁最大的深水地质灾害之一。然而，海底蠕变区的形成机理和不稳定性目前仍未得到充分揭示。为此，本项目以南海北部珠江口盆地东南部陆坡的海底蠕变区为研究区域，通过大量地球物理资料解释、沉积物样品分析和数值模拟相结合的方法尝试揭示其形成机理并定量分析其不稳定性。首先，通过地形地貌分析和三维地震解释获得海底蠕变区的内部地质结构，建立初始地质模型；其次，通过对沉积物样品进行测试和分析，为数值模拟海底蠕变区的形成过程提供约束条件；最后，数值模拟海底蠕变区浅地层的变形过程，并计算浅地层的不稳定性系数，揭示海底蠕变区的形成机理及不同控制因素对浅地层蠕变的影响作用。本研究完成后不仅可望在理论上能够促进海底蠕变及海底滑坡成因机制的研究，而且也有利于南海北部陆坡区的深水地质灾害评估。

海底蠕变是海底浅地层在重力荷载驱动下发生缓慢的、持续的、长期不可逆转的海底变形现象，地貌上表现为一系列隆起和沟槽相间排布。这些沟槽和隆起的形成与陆坡的不稳定性及重力滑移有关，未来可能演化为大规模的海底滑坡。海底蠕变及其造成的海底失稳（海底滑坡）已逐渐成为严重威胁海洋工程设施甚至人类生命安全的最主要深水地质灾害。然而，与海底滑坡相比，海底蠕变的成因机制目前仍未得到充分揭示。因此，查明南海北部珠江口盆地海底蠕变的分布规律、成因机制及控制因素等，有助于为海底管道铺设、海上钻井平台等工程设施的设计、施工提供科学依据，对于保障南海北部深水油气的安全开发具有重要应用价值。此外，我们研究发现海底蠕变是海底滑坡发生的前兆，对南海北部珠江口盆地海底蠕变形成机理的研究能够为我国南部沿海的海啸预警提供重要的理论依据。为了厘清珠江口盆地海底蠕变的成因机制和控制因素，本项目的研究工作主要聚焦于珠江口盆地陆坡两个典型海底蠕变区，我们精细刻画了海底蠕变的地形地貌特征和内部地质结构，建立了海底蠕变区的地质几何模型，对采集自西南陆坡海底蠕变区的浅层沉积物样品进行了物理力学测试分析，确定了海底蠕变数值模拟所需的物理力学参数，最终完成了海底蠕变过程的数值模拟以及不稳定性分析，为揭示海底蠕变的形成机理以及确定其灾害风险提供了重要的科学依据。本项目的研究成果揭示了南海北部珠江口盆地海底蠕变的成因机制与控制因素，有助于更好地理解海底蠕变的形成过程及动力学机制，能够为深水地质灾害风险科学评估、海洋工程设施防灾减灾及深水油气与天然气水合物勘探开发提供理论依据，并对提高我国海洋工程地质安全性具有一定的理论意义和应用价值。