What is the mysterious and terrible earthquake and tsunami?

Due to earthquakes, volcanic eruptions, landslides in island arc areas and landslides in coastal areas on the seabed or continental margins, seawater fluctuates violently. People call it an earthquake and tsunami. The tsunami caused by landslides is called "landslide wave" in some countries.

The wavelength of earthquake and tsunami is very long, ranging from tens of kilometers to 500-600 kilometers, and the propagation speed is fast. In the ocean with a water depth of three or four kilometers, it can spread dozens of kilometers per hour, sometimes even hundreds of kilometers. In addition, when earthquakes and tsunamis spread in the ocean, the wave height is generally 1 ~ 2 meters, and the wavelength is very long, so it is not easy to be detected. But in shallow water or near shore, the waves overlap and the peaks rise, some as high as 20 meters and the highest as 40 meters. At this time, due to the continuous concentration of wave energy, its great destructive power is unimaginable. According to the actual measurement, the wave pressure of the earthquake and tsunami on the affected coast can reach 20 ~ 30 tons per square meter; A tsunami occurred in the Bay of Biscay in the United States, and the wave pressure reached 90 tons per square meter. It is not difficult to imagine that strong earthquakes and tsunamis will pose a great threat to people and property in some coastal countries and regions, and will also cause irreparable losses to areas where earthquakes and tsunamis occurred and even disaster-stricken areas.

Whenever an earthquake occurs, the sharp rise and fall of the seabed crust will force a column of seawater thousands of meters deep to move, and at the same time form huge and rapid waves in the upper seawater. When the waves flood into the shallow water area, the waves will suddenly increase and slow down, stand upright like a giant in the sea and dump on the shore like a wall. If you encounter a funnel-shaped deep-water harbor canyon, or go upstream along the river valley, the tsunami waves will be bigger and fiercer, and the high water wall will rush in like lightning and devour all the houses, trees, people and animals along the way. Immediately, the tsunami wave retreated with everything it swallowed, and then came back. Going back and forth like this several times is like destroying everything, and all obstacles will be removed.

Sometimes the sea water flows away sharply, forming a big low tide, exposing the offshore seabed reef that has never been seen before. Then, the sea rose violently again. This situation is generally a tsunami formed by the rapid collapse of the seabed crust. On the contrary, if the tsunami wave reaches the coast first and impacts the coast like a water retaining wall, then this tsunami is generally caused by the sharp uplift of the seabed crust.

Hawaiian fishermen witnessed an unprecedented spectacle on 1 April, 9461day: the sea water receded sharply, the unexposed seabed was suddenly exposed in broad daylight, and many marine fish and marine life jumped around the seabed. Thinking that a miracle had happened, these fishermen scrambled to catch fish. Results A sudden wave made 1 19 people die in the belly of fish. This incident made people realize that when the sea suddenly falls, they should be alert to the "earthquake and tsunami" attack.

According to historical records, on 1 June 755 1654381October1day, a major earthquake occurred in Lisbon, the capital of Portugal, which is located on the Atlantic Ocean and the European coast, and it also triggered a tsunami. I saw that the sea receded first, and the huge wave was as high as 18 meters. A large number of buildings near the coast were destroyed by rough waves and many ships sank. The buildings in Lisbon were destroyed in almost six minutes, 65,438+10,000 people died in huge waves, and a bustling city instantly turned into ruins.

There are two most famous earthquakes and tsunamis in history. Once in the Mediterranean. About BC 1450, there was a Schiller Island in the southeast of Greece. Due to the volcanic eruption, the whole island was thrown into the air and then fell to the bottom of the sea. The huge tsunami destroyed the Miro culture on Schiller Island. Some scholars believe that the story of Moses' dividend distribution in the sea in the Bible is related to this tsunami, and Bellagio's "Daxi" is also based on this. Another huge earthquake and tsunami is the earthquake and tsunami in Lisbon, Portugal mentioned above. The tsunami wave caused by this earthquake is nearly 30 meters high. It was Halloween, and many believers prayed in church, but they were not spared. This tragedy has aroused many people's doubts about religious belief. Rousseau, a French enlightenment thinker, once cited this example to persuade people not to join the church.

1883 On August 27th, Krakato volcano erupted near Sumatra, Indonesia, which triggered the largest earthquake and tsunami in modern history. The ensuing huge waves reached more than 30 meters, wiping the whole village off the map, and the death toll reached 36,000. After 1890, the Akita earthquake and tsunami in Japan also killed 27,000 people, destroyed more than 20,000 houses and flooded a large area of land.

1960 from may to June, a series of major earthquakes occurred on the seabed near Chile in south America. Among them, 10 exceeded level 7 for three times and level 8 for three times. The strongest one, with a magnitude of 8.9, occurred in Chiloe, Chile, and triggered the largest tsunami in the world. 1960 On May 23, an earthquake of magnitude 8.9 occurred on the seabed of Chile, which immediately caused changes in the seabed crust within 700 kilometers. The epicentre crust rose by 3-4 meters at maximum and sank by 2 meters at maximum. The sensing range of the earthquake exceeds 1000 km. Due to the sharp rise and fall of the seabed crust, the sea water rose and fell, and a tsunami occurred. The average wave height of this tsunami on the 500km coast of Chile is10m, and the maximum wave height is 25m. Of course, as far as the height of tsunami wave is concerned, it is not the highest among earthquakes and tsunamis, but its scope and energy are incomparable with other tsunamis.

After the tsunami, it first rushed to the coast of Chile, destroying port facilities and engulfing fishermen's villages and towns, leaving thousands of people devastated and tens of thousands homeless. The huge waves caused by the tsunami rushed to the whole Pacific Ocean at an extremely fast speed, and rushed to New Zealand and Australia in the South Pacific Ocean, forming a powerful vortex in Sydney Harbour, causing huge losses to ships in the harbor. The tsunami hit the coasts of the Philippines, Hawaii and Japan. At an average speed of 707 kilometers per hour, it took only 14 hours and 56 minutes to cover the distance of 1660 kilometers and reach the Hawaiian Islands in the Pacific Ocean, which is almost comparable to the speed of an airplane. The tsunami wave height observed in Hawaii is 9 meters. When it took 2 1 more hours to drive 17000 km to reach Japan, the maximum wave height was still 8.l meters. The tsunami looted the Pacific coast of Honshu Island, Japan, and filled the entire coast of a place in northern Japan with the wreckage of various ships.

Before the tsunami in Chile reached Japan, despite warnings and preparations, it still caused considerable damage, destroying more than 65,438+0,500 houses and causing 1 0,000 casualties. The tsunami hit Wan Li, but its power is not diminished, and it still maintains great destructive power. The tsunami affected the Sea of Okhotsk in the former Soviet Union before withdrawing troops and returning to camp.