Development of an early detection method for near field tsunamis

这项研究的一个目标是开发一种近场海啸的早期检测方法。为此目的，对海啸的产生机制、瑞利波的利用以及海啸前的海面扰动进行了调查，结果如下。关于海啸、瑞利波和海面扰动之间的关系。最近发展了一种在流体域中同时考虑断层破裂和Navier-Stokes方程来估计动态地面位移的海啸动态模拟方法。利用该方法研究了海啸、瑞利波和海面扰动之间的关系，为早期探测奠定了基础。在瑞雷波传播特征方面，从动力海啸模拟中发现，断层前缘地区瑞雷波的波幅和海面扰动都比其他地区大。尤其是沿断层破裂传播方向的振幅明显较大。利用1993年北海道南关海啸的潮汐记录和1999年集集台湾地震的强震记录，研究了强震的传播幅度和传播方向，证实了上述特征。在动态模拟中，采用SOLA-SURF方法进行流体域模拟，由于该方法的局限性，只允许垂直壁面条件。因此，为了模拟海啸启动，我们取消了使用VOF和嵌套方法的限制。

An objective of this research is to develop an early detection method for near field tsunamis. For this purpose, the tsunami generation mechanism, the use of the Rayleigh waves and the sea surface disturbance preceding tsunamis has been investigated, with the results shown below.1. On the relationship among tsunamis, Rayleigh waves and sea surface disturbance.The dynamic tsunami simulation method that estimates both the dynamic ground displacement considering the fault rupturing and Navier-Stokes equation in fluid domain has recently been developed. Using the method, the relationship among tsunamis, Rayleigh waves and sea surface disturbance has been investigated for the early detection.2. On the characteristics of Rayleigh wave propagation.From the dynamic tsunami simulation, the amplitude of the Rayleigh waves and the sea surface disturbance has-been found to become larger in the front area of the fault than that in other area. Especially, the amplitude is remarkably larger in the direction of the fault rupture propagation. Using tidal records in 1993 Hokkaido Nansei-Oki tsunami and the strong motion records in 1999 Chi-Chi Taiwan earthquake, the amplitude and the direction of the propagation have been investigated to confirm the above-mentioned characteristics.3. On tsunami run-up simulation using the VOF and the Nesting technique.In the dynamic simulation, SOLA-SURF method was used in fluid domain simulation, where only vertical wall conditions are allowed because of the limitations of the method. Thus, to simulate the tsunami run-up, we have removed the limitations using of the VOF and the Nesting method.