A Study On Tsunami Modelling And Estimation Of Wave Amplitude

Tsunami is a phenomenon of violent fluctuation of sea surface at coastal region,which is triggered by earthquake of seafloor,eruption of volcano at seabed and falling down of meteorite.Several tsunamis that cause serious disaster happened at the beginning of 21 th century,such as Indian Ocean tsunami evoked by Sumatra' earthquake in 2004 and Pacific Ocean tsunami caused by Japanese earthquake in 2011.Tsunami wave leads to serious economic loss and death of people in coastal region near the epicenter of earthquake.Furthermore,it propagates rapidly across the ocean,and destroys cities and harbors far from the epicenter.There are two methods to research wave height of tsunami.One is analysis of historical tsunami's records and the other is numerical computation.This paper concentrates on tsunami modelling by numerical model based shallow water equations and establishing an empirical formula to evaluate tsunami amplitude through numerical experiments.It has practical significance for early warning of potential tsunami.Firstly,2011 Japan Tohoku tsunami is simulated by nonlinear shallow water equations.The numerical model,GeoClaw,adopts on finite volume method to discretize governing equations.DART buoy's data is used to validate numerical model in terms of time series of surface elevation.Next,several cases with different earthquake parameters and fault length-width ratios are considered to establish an ideal basin model for numerical experiments.Okada model is used to generate seafloor deformation and resultant initial wave field condition for earthquaketriggered tsunami.Propagation of earthquake-triggered tsunami on flat seafloor of 4000 m water depth is simulated.Time series of wave amplitude in monitoring points located in different distance and azimuth from the epicenter are analyzed.An empirical formula is proposed for calculating wave amplitude of tsunami.Then,it is used to calculate wave amplitude at DART buoy's sites due to 2011 Japan tsunami.The empirical formula is also applied to prediction of tsunami amplitude at contour line of 500 m depth in a tsunami induced by a potential earthquake in Manila trench of South China Sea.Finally,Inundation of Sanya city in Hainan of China is computed numerically and the effect of Manning coefficient on computed inundation area is investigated for case of extreme tsunami in South China Sea.