Numerical Investigation On Tsunami Inundation

As a kind of surface gravity wave occurring in the ocean, tsunami could begenerated by underwater earthquakes, landslides, volcanic eruptions, icebergs, andmeteorite, and usually consists of a sequential of serious waves. In contrast with thecommonly occurring ocean waves, such as wind wave, tidal wave, andcurrent-induced waves, tsunami has longer wavelength and propagates faster. Thewave propagation speed of tsunami is dependent on water depth. As it approaches theshallow water in coastal area, its propagation speed is getting slower, while its waveheight begins to increase dramatically. Obviously, tsunami is a threat to people livingin the coastal area and their properties. As tsunami reaches3to6m high, it isbecoming considerably destructive to human beings. So far the reported maximumtsunami is able to reach over40m.In the past decade, huge tsunami events occur frequently in the global oceans.For instance, Indian Ocean tsunami in2004and Japan tsunami in2011, have causedextremely serious hazards, leading to that lot of coastal countries pay much moreattention to the tsunami and its disasters. Therefore, the investigation on tsunami isvery significant to the issue of disaster prevention and reduction, especially theevaluation of tsunami disaster. If we could estimate the probable damage by tsunamipriori to its arrival, the tsunami disaster would be reduced by the prepared emergencyplan.In the Pacific Ocean and its marginal areas, the frequency of tsunami occurrenceis very high. Averagely speaking, one tsunami event occurs within a couple of years inthis area. China is located in the western Pacific Ocean, facing the risk tsunami fromlocal, regional and cross-ocean tsunami events. The coastal regions in China areeconomically developed areas, and usually suffering from tsunami disaster as well.Almost half of large and medium-sized cities in China are located in the coastal zone. Numerous infrastructures have been constructed along the coast, such as ports,nuclear power stations, petrochemical projects, and so on. If tsunami occurs in Chinacoasts, it is foreseeable that the disaster would be very serious in the absence of theemergency plan on the basis of the detailed and systematical investigation on tsunami.The present dissertation is focusing on the tsunami inundation in Shantou urbanarea. On the basis of analyses to the submarine seismic data surrounding Shantouurban area, the seismic foci which are likely to trigger off tsunamis affecting Shantouurban area are figured out. Combining with the analysis to geological tectonic beltswhere the seismic foci are located, the hypocenter parameters are obtained. Usingthese hypocenter parameters, the tsunami waves affecting Shantou urban area aresimulated with numerical model.So far the high resolution datasets in topography and bathymetry required by thenumerical model is unavailable yet, the used dataset is obtained by merging with GIStechnique several commonly used datasets, out of which the datasets with highresolution and small error are selected. The bathymetric dataset is revised with thenear-shore data obtained by ‘908’ project. Owing to the limitation of the elevationmeasurement technology, usually the sea and land border line is fuzzy and inaccurate.The Landsat satellite image data is used to solve this problem.The used model is the COMCOT model, which is developed by CornellUniversity, in terms of shallow water equations, with the option of the sphericalcoordinates or Cartesian coordinates. In the COMCOT model, an explicit leap-frogdifferencing scheme is used to solve shallow water equations. The multi-nested grid isused in the model, so that the modeling accuracy is guaranteed and the computer timeis saved.Priori to the application to Shantou urban area, the model was verified withJapan tsunami event in2011. It is shown that the model results of tsunami inundationare agreeably consistent with the observational data by the disaster investigation teamfor Japan tsunami in2011.Then, the numerical model is used to simulate the tsunami inundation in Shantou.In the simulation the tidal effect is considered as well. After that, analyse the calculation results comparatively. The numerical results show that Shantou urban areais suffering from the risk of tsunami inundation indeed, and the most dangerous threatis originating from the earthquake in Manila trench. It is also indicated that theinundation area could be doubled, while the tsunami wave height varies trivially, byconsidering the tidal effect.Finally, combining numerical results and the environmental database of Shantouurban district together, and the tsunami inundation map using GIS software isobtained.