Development of an early detection method for near field tsunamis

本研究的目的之一是发展一种近场海啸的早期检测方法。为此，对海啸的产生机制、瑞利波的利用以及海啸发生前的海面扰动进行了研究，结果如下：1。论海啸、瑞利波与海面扰动的关系。近年来发展了考虑断层破裂和流体域Navier-Stokes方程的地震海啸动态模拟方法。利用该方法研究了海啸、瑞利波和海面扰动之间的关系，为海啸的早期检测提供了依据。瑞利波传播特性研究。从海啸动态模拟中发现，瑞利波的振幅和海面扰动在断裂带前缘比其他区域更大。特别是在断层破裂扩展方向上，振幅明显较大。利用1993年北海道南井冲海啸的潮汐记录和1999年台湾集池地震的强震记录，对其振幅和传播方向进行了研究，证实了上述特征。基于VOF和嵌套技术的海啸上升模拟。在动态模拟中，流体域模拟采用了SOLA-SURF方法，由于该方法的局限性，只允许垂直壁面条件。因此，为了模拟海啸的上升，我们已经消除了使用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.