The hazards brought by earthquake and tsunami to mankind are enormous. After a violent shaking, the waves roared across the shoreline and across the fields, rapidly attacking cities and villages on the shore. All port facilities, collapsed buildings, will be swept away by the waves. Afterwards, the beach was a mess of broken wood and human and animal carcasses. At present, human beings can only prevent or reduce the losses caused by earthquakes, volcanoes, tsunamis and other sudden disasters through prediction and observation, but can not control their occurrence.
On December 26, 2004, a tsunami triggered by an 8.9 magnitude earthquake off the coast of Sumatra Island, Indonesia, affected more than 10 countries in Southeast Asia, South Asia and East Africa. Indonesia, Sri Lanka, India, Thailand and other countries suffered the most serious disasters. It was also the worst tsunami disaster in human history since records began. The total number of victims of the Indian Ocean tsunami has exceeded 280,000. According to the USGS, the tsunami released energy equivalent to 23,000 atomic bombs dropped on Hiroshima at the end of World War II.
In 1960, after an 8.9 magnitude earthquake in Chile (moment magnitude 9.5), the tsunami wave swept across the western Pacific islands at a speed of 700km/h and reached the Hawaiian islands in the United States only 14 hours later. When it arrived in the Hawaiian Islands, the waves reached 9 to 10 meters, destroying the breakwater on the West Bank of the island, toppling a large number of trees, poles, houses and construction facilities along the breakwater, and flooding a large area of land. In less than 24 hours, the tsunami wave covered about 17,000 kilometers, reached the Japanese islands on the other side of the Pacific Ocean. At this time, the waves are still very turbulent, waves up to 6〜8m, the largest up to 8.1m, the rolling waves rage through the coastal cities of Japan's islands.
The magnitude of tsunami hazards in coastal areas is mainly affected by seabed topography and terrain, if the depth of sea water decreases rapidly from ocean to land, and the coastal land is flat and the altitude is low, then even small tsunami waves are prone to large tsunami disasters. Therefore, in coastal planning and construction, we should avoid these areas as far as possible.
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