南海海啸数值模拟研究

发布时间：2018-08-24 10:57

【摘要】：海啸是一种具有突发性和强大破坏力的海洋灾害,本世纪初发生的2004印度洋海啸和2011日本海啸产生的巨大灾害引起了全球范围的高度重视。海啸一般是由海底地震、滑坡,或火山喷发等引起海底剧烈震动和变形,进而引发海水表面的巨大扰动形成海啸波向四周传播。海啸波在抵达近岸时,由于水深变浅,波高迅速增加,对海岸带产生剧烈的破坏作用。本文旨在利用可靠的数值模型,模拟研究海啸生成、传播和对近岸的影响,分析南海潜在海啸源对周边地区的影响,研究南海海啸数值预警方法和针对马尼拉海沟地震海啸的快速预警技术,为南海海啸预警与防灾减灾提供科学依据。首先,利用Okada弹性半空间位错理论模型,研究了走向角、倾角、滑移角、震源深度,和滑移量等震源参数对海底地形的抬升和沉降的影响规律。针对真实地震产生的复杂海底变形,采用多个单元板块线性叠加的方法模拟地形的演变或给出每个板块运动时间,可以用来描述真实的地震引发的海底变形的复杂变化过程。针对本文运用的基于非线性浅水方程模拟海啸波传播的数值模型(GeoClaw),详细介绍了控制方程和数值方法。从一维非线性浅水方程出发,结合双曲守恒律和线性化理论,在有限体积法的基础上构造离散格式,对方程进行数值求解。自适应网格技术是该模型的一个特色,可以根据海啸波波高进行追踪判断是否对网格进行加密。对于海啸越洋传播这样的大尺度计算问题,该方法可以有效提高计算效率,较快得到模拟结果。基于建立在非线性浅水波方程基础上的数值模型,分别对溃坝问题、柱面波的传播、液体的三维晃荡问题、高斯波对岸坡的影响等基本算例进行验证计算。通过与解析解、实验结果的比较,验证了模型的计算精度;通过不同类型网格的数值计算结果比较,验证了自适应网格的有效性。结果表明该模型可以有效地模拟浅水波的传播;在保证计算精度的前提下,自适应网格技术可在一定程度上提高计算效率。以2004印度洋海啸和2011日本地震海啸为例,对基于有限体积法的二维非线性浅水方程数值模型进行验证计算。通过与浮标实测数据的比较,表明该模型可以较为准确地模拟真实海啸。根据数值模拟结果分析了这两次海啸的传播特征。通过对不同震源的模拟,比较不同精度的震源对数值结果的影响,发现高精度震源参数可以得到更好的结果。进一步利用更精细的网格,研究日本大海啸对仙台地区的淹没影响,数值模拟结果与实测结果吻合较好。数值结果表明,由于海啸特殊的传播路径和东海大陆架较浅的水深,2011日本海啸对中国沿海的影响不大,近岸最大波高仅有0.5m。根据马尼拉海沟的断层分布特征,总结了一般震级的震源参数特征和特大地震的震源参数特征。利用数值模型模拟研究八级地震时,不同板块诱发海啸的传播特征和影响范围,并分析对海南岛、台湾岛和伶仃洋等局部区域的影响。进一步针对马尼拉海沟可能发生的mw=9.3级特大地震,模拟计算了南海特大地震海啸的传播特征和影响范围,以及对海南岛、台湾岛和伶仃洋等产生的影响,并分析了海啸产生的流场特征。利用boussinesq模型,计算了南海mw=8.0级和mw=9.3级海啸的传播,通过比较考虑色散和不考虑色散的计算结果,发现南海潜在海啸的色散效应并不明显。针对南海马尼拉海沟潜在震源区可能发生的海啸,模拟计算了单元板块发生单位滑动所引发的海啸,并构建了相应的海啸源数据库;建立了一套基于多个浮标监测数据和最小二乘法的海啸反问题预警方法,并应用于南海马尼拉海沟潜在震源的海啸预警。通过与正问题模拟结果的比较,验证了该预警方法的有效性。本文发展的基于多浮标反演方法在预警震级较高、范围较大的南海马尼拉海沟地震海啸比单浮标方法有更高的可靠性。鉴于浮标的成本,利用数值模拟结果给出了优先布置的浮标位置。结合马尼拉海沟潜在震源断裂带分布的基本特征,建立一种针对马尼拉海沟突发海啸进行快速预警的方法,可以在5 min给出马尼拉海沟地震激发海啸的可视化数值模拟结果,为南海海啸快速预警和海啸防灾减灾提供依据。
[Abstract]:Tsunami is a kind of marine disaster with sudden and strong destructive power. The huge disasters caused by the Indian Ocean tsunami in 2004 and the tsunami in 2011 have attracted great attention all over the world. Tsunamis are usually caused by seabed earthquakes, landslides, or volcanic eruptions, which cause severe vibration and deformation of the seabed, and then trigger the surface of the sea water. The tsunami waves propagate around the coastal zone because of the shallow water depth and the rapid increase of wave height when they reach the coastal zone. This paper aims to simulate the generation, propagation and impact of the tsunami on the coastal zone by using a reliable numerical model, and to analyze the impact of potential tsunami sources in the South China Sea on the surrounding areas. The numerical early warning method for the South China Sea tsunami and the rapid early warning technology for the earthquake and tsunami in Manila trench provide scientific basis for the early warning and disaster prevention and reduction of the South China Sea tsunami. In view of the complicated seabed deformation caused by real earthquake, the evolution of terrain is simulated by using the method of linear superposition of multiple plates or the movement time of each plate is given. The complex process of seabed deformation caused by real earthquake can be described. The nonlinear shallow water equation model is used in this paper. A numerical model of tsunami wave propagation (GeoClaw) is introduced in detail. Based on one-dimensional nonlinear shallow water equation, combined with hyperbolic conservation law and linearization theory, a discrete scheme is constructed on the basis of finite volume method, and the equations are solved numerically. For large-scale computation problems such as tsunami transoceanic propagation, this method can effectively improve the computational efficiency and get the simulation results quickly. Based on the numerical model established on the basis of nonlinear shallow water wave equation, the dam-break problem, the propagation of cylindrical wave, and the liquid problem are respectively solved. Three-dimensional sloshing problem, the influence of Gaussian wave on bank slope and other basic examples are validated. Comparing with analytical solution and experimental results, the calculation accuracy of the model is verified. Comparing the numerical results of different types of meshes, the validity of the adaptive mesh is verified. The results show that the model can effectively simulate the propagation of shallow water waves. Taking the Indian Ocean tsunami in 2004 and the local earthquake tsunami in 2011 as examples, the two-dimensional nonlinear shallow water equation numerical model based on the finite volume method is validated and calculated. In order to simulate the real tsunami accurately, the propagation characteristics of the two tsunamis are analyzed according to the numerical simulation results. By simulating different sources and comparing the influence of different precision sources on the numerical results, it is found that the high precision source parameters can get better results. Further more, the Japanese tsunami on Sendai is studied by using a more refined grid. The numerical results show that due to the special propagation path of the tsunami and the shallow water depth of the East China Sea continental shelf, the impact of the 2011 tsunami on China's coast is not significant, and the maximum wave height near the coast is only 0.5m. Focal parameter characteristics and focal parameter characteristics of extraordinarily large earthquakes.The propagation characteristics and influence range of tsunamis induced by different plates during M8 earthquakes are simulated by numerical model,and the effects on Hainan Island,Taiwan Island and Lingding Ocean are analyzed.The possible Mw=9.3 earthquake in Manila trench is further simulated. The propagation characteristics and influence range of the tsunami and its effects on Hainan Island, Taiwan Island and Lingdingyang are calculated, and the characteristics of the flow field generated by the tsunami are analyzed. The propagation of the tsunamis of magnitude mw=8.0 and magnitude mw=9.3 in the South China Sea are calculated by using Boussinesq model. The results of the calculation are compared with those of the calculation with and without considering dispersion. The dispersive effect of potential tsunamis in the South China Sea (SCS) is not obvious. For the potential tsunamis in the Nila trench, the tsunamis caused by unit slip of the unit plate is simulated and calculated, and the corresponding tsunami source database is constructed. The early warning method is applied to the tsunami warning of potential earthquake sources in the Nila trench of the South Hippocampus.The effectiveness of the method is verified by comparing with the simulation results of the positive problem.The inversion method based on multiple buoys developed in this paper is more reliable than the single buoy method in predicting the earthquake tsunami in the Nila trench of the South Hippocampus with higher magnitude and larger range. In view of the cost of buoys, the location of buoys with priority is given by numerical simulation results. Combining with the basic characteristics of the distribution of the potential source fault zone in Manila trench, a rapid early warning method for the sudden tsunami in Manila trench is established. The visualized numerical model of the tsunami triggered by the Manila trench earthquake can be given in 5 minutes. The results provide a basis for the rapid tsunami warning and tsunami disaster prevention and mitigation in the South China Sea.
【学位授予单位】：上海交通大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：O241.82

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