The Numerical Simulation Study Of Indonesia Tsunami And Its Hazard Assessment

In this paper based on a global ocean model GOCTM derived from FVCOM a tsunami numerical model is built up. Using the tsunami source as the initial surface elevation condition which is provided by Alfred Wegener Institute (AWI) in Germany, the tsunami event generated by the great Sumatra–Andaman earthquake on 26 December 2004 was simulated with the model GOCTM. In order to simulate the tsunami under the tide, equilibrium tide module is open.GOCTM takes advantage of the finite-volume discrete method to solve the 3-D primitive equations and the geometric flexibility of unstructured triangular. Meanwhile, no open boundary condition is considered in GOCTM that avoids the uncertainties to the simulation. After a series of test, GOCTM can be used in simulation of tsunami propagation.The seafloor displacement caused by an earthquake event is computed via elastic finite fault plane theory. Approximately the surface elevation of ocean is equal to the displacement of the sea floor as the force of the propagation simulation. In this paper the initial elevation data as tsunami source on 26 December 2004 is provided by AWI. The data was interpolated into the triangular grid as the initial elevation condition of the model. When the tide is needed, the elevation and velocity of the tide at some time are added to the initial conditions. As comparison the rising tide near western coast of Sumatra is needed to simulate the tsunami propagation under the tide.In order to check the result, we compare model results to tide gauge data from all around the Indian Ocean, to satellite altimetry in selected track.Finally we got the conclusions as follows: (1) The tsunami reaches the north part of the Sumatra approximately 25 minutes after the earthquake. The sea surface elevation is about 4 meters. The arrival time coincides with the results of TUNAMI model and TsunAWI model. The tsunami can affect the coast of Indian Ocean. The waves would be reflected between Andaman islands and western islands of Sumatra that increase the amplitude of the elevation. (2) The arrival times of the tsunami wave are coincided with the data comes from tide gauge data along India and satellite altimetry data. Although the amplitude of the model data is lower than actual measurement data. (3) When the tsunami under the effect of the tide, the sea surface elevation along the coast are affected by the tide. This result would bring the uncertainty to the forecast of the tsunami. (4) The comparison between three experiments shows that the arrival time and wave form are not affected by the tide except surface elevation. But the change of the elevation caused by the tide can be considered as linear combination between tidal level and tsunami. So when we forecast the tsunami, we can consider the forecast of tsunami and tide at the same time.At the last part of the paper, some suggestion and problems about the system of tsunami forecast and warning are given. The first task is to build the data base of the tsunami in the potential earthquake zones.