南海典型海底滑坡的触发机制及其潜在海啸灾害评估

Triggering Mechanism and Tsunamigenic Potential of Typical Submarine Landslides in South China Sea

综合调查数据揭示南海域内发育大量海底滑坡,尤其是大陆坡区域。由海底滑坡触发的碎屑流、浊流和海啸等链生灾害,严重威胁深海基础设施及沿海地区人民生命财产安全,亟待进行研究。选取南海域内4处典型海底滑坡,研究其潜在的海啸灾害。在总结各滑坡构造背景和触发因素差异的基础上,提取各滑坡体的特征参数;使用NHWAVE与FUNWAVE-TVD模型组合模拟了滑坡体动态过程及海啸波的产生和传播过程。模拟结果显示,初始水深和坡度差异导致体积相近的白云滑坡和曾母暗沙滑坡触发海啸能力差异巨大。白云滑坡在源区可产生最高约12 m的海啸波,潜在灾害主要危及南海北部区域,尤其是华南沿海;位于较浅初始水深的曾母暗沙滑坡可产生高达约38 m的海啸波,危及整个南海中南部;中建南滑坡可产生近10 m的海啸波,影响范围主要局限于南海西部越南沿岸;西沙海槽北部陆坡滑坡产生的海啸波波高相对较小,约0.9 m。通过分析比较最大波高分布和海啸波传播特点等,发现海底滑坡触发海啸能力受到滑坡几何参数与运动学特性控制,复杂海底地形和海岸线改变了海啸波的能量分布,增加了沿岸海啸灾害评估难度。在南海开展典型滑坡—海啸模拟,建立滑坡—海啸数据库具有重要的研究意义,将有助于推进我国海洋地质灾害评价与预测水平。

High-resolution geophysical data indicate that there are numerous submarine landslides in the China Sea region at various scales,particularly on continental slopes.Potentially devastating tsunami hazards generated by submarine landslides pose a great threat to the populous coastal region,fisheries,and oil and gas exploitation in the deep sea.Thus,hazard assessment is necessary.This study investigates the potential tsunami hazards generated by four representative submarine landslides in the South China Sea(SCS).The geological background and triggers of these submarine landslides are summarized.The key parameters of each landslide were constrained by currently available geological and geophysical data.A combined modeling approach,NHWAVE and FUNWAVE-TVD,was used to model the dynamic process of landslide movement and the generation and propagation of landslide tsunamis.The simulation results show that the tsunamigenic capacities of the Baiyun and Zengmu Ansha Slides differ significantly,although they have comparable volumes.This large difference was attributed to the discrepancy in the initial water depth and slope gradient.Tsunami waves generated by the Baiyun Slide rose up to approximately 12 m in the source area and mainly affected the northern region of the SCS,particularly the southern mainland Chinese coast.The Zengmu Ansha Slide generated 38 m tsunami waves that assailed the majority of the coastline of the southern SCS.The Zhongjiannan Slide generated highly localized tsunami waves about 10 m near the source region on the west SCS coast.The North Xisha trough slide produced a minor tsunami impact with tsunami waves that were approximately 0.9 m high in the source region.The distribution of the maximum surface elevation and the propagation characteristics of tsunami waves suggest that the tsunamigenic potential of submarine landslides is controlled by geometric and kinematic parameters.Meanwhile,complex bathymetry and coastlines change the energy distribution of tsunami waves,increasing the difficulty of tsunami hazard assessment.Conducting landslide-tsunami simulations for typical landslides in the SCS and establishing a landslide-tsunami database is of great research significance and will assist in improving the prediction of marine geo-hazards in China.