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How to deal with the 15th anniversary of the Indian Ocean tsunami?

Original title: 15th anniversary of the Indian Ocean tsunami: about 300000 dead and 500000 homeless

4hw.com.cn on December 26, 2004, an earthquake with a magnitude of 9.1 on the Richter scale occurred near Sumatra island, Indonesia, which triggered a large tsunami, causing heavy losses of public life and property in countries along the Indian Ocean coast, killing nearly 300000 people and leaving more than 500000 homeless. The extent of its destruction and the scope of its influence are rare in human history.

After the tsunami, the British media had such a report.

·, a 10 year old British girl who came to visit a beach in Phuket Island in Thailand before the tsunami hit Smith, was keenly aware that the distant sea was suddenly not calm, the sea began to froth, the speed of the water flow was accelerating, and the speed was dropping back.

Based on what she learned in her geography class about the tsunami, Tilly quickly recognized the signs of the coming tsunami, and let her parents give an early warning to evacuate the tourists on the beach, thus saving the lives of more than 100 tourists and performing a legend.

How much do you know about earthquakes and tsunamis over the past 15 years?

How to deal with the tsunami?

Today, I'd like to invite Chen Zhen, academician of the Chinese Academy of Sciences and director of the science and Technology Committee of the China Seismological Bureau, researcher Ding Zhifeng, deputy director of the Institute of Geophysics, CSB, and Zhang Xiaodong, deputy director of the Institute of earthquake prediction, CSB, to tell us about earthquakes and tsunamis--

What happened 15 years ago today?

Tsunami is a kind of catastrophic wave, which is caused by the sudden changes of seabed topography such as submarine earthquake, submarine volcanic eruption, submarine debris flow, landslide and so on.

Earthquake tsunami is a large vertical movement of the sea floor when an earthquake occurs in the ocean, which causes the whole sea water to rise sharply and propagate outward, resulting in a tsunami.

Tsunamis can travel a long distance, usually several thousand kilometers, but the energy attenuation is very small, so it may cause tsunami disasters in places thousands of meters away.

The coast of Sumatra, Indonesia, is where the Indo Australian plate collides with the Asian plate.

When an earthquake occurs, the long-term accumulated elastic energy is released instantaneously. One of the plates rapidly thrusts onto the other plate, and the sea water of thousands of meters long, hundreds of kilometers wide and thousands of meters deep is lifted several meters in an instant, and then propagates outward in the form of waves. This is the process of the Indian Ocean tsunami.

'the epicenter of the Indonesian earthquake was an uninhabited sea, and the earthquake itself caused not many casualties. However, the tsunami caused by the earthquake hit the densely populated coastal zone hundreds or thousands of meters away, so the disaster was serious. "Academician Chen said that the tsunami triggered by the Indian Ocean earthquake has affected Indonesia, Sri Lanka, Thailand, India, Malaysia, Bangladesh, Myanmar, Maldives and other countries, resulting in greater casualties and property losses.

According to the U.S. Geological Survey geist model, the tsunami wave generated by the Indonesian earthquake only takes 2-3 hours to reach Sri Lanka and India, which is as fast as a jet plane.

Throw small stones into the water, and the water will ripple. The longer the wavelength is, the more seawater is involved in the movement. The shorter the wavelength is, only a thin layer of water on the surface of the sea participates in the wave motion. According to academician Chen, the JASON-1 altimetry satellite at that time passed through the Indian Ocean from south to North in orbit 129 two hours after the earthquake and approached Bengal Bay of India. At this time, the tsunami wave just propagated over the Indian Ocean, and the measured wavelength of the Indian Ocean reached about 500 km. "You should know, the deepest Mariana Trench on the earth is only about 10 km away, which causes huge impact force Big one. '

'it was as if the coast had been emptied, leaving bare ground. "Zhang Xiaodong, who had participated in the earthquake rescue in Indonesia, recalled that after the tsunami, huge waves hit towns and destroyed houses in an instant. At one time, the debris was washed ashore for three or four kilometers.

"The tsunami is more serious than the collapse of houses caused by the earthquake. There are still gaps left in the collapse of houses, and people can breathe. But the tsunami happened within minutes, and there was no time to hide. '

Do earthquakes and tsunamis occur frequently in the world?

There are not many large earthquakes with magnitude 9 or above in the world. There were about 12 earthquakes in the 170 years from 1833 to 2011. Earthquakes with M = 9 and above belong to giant earthquakes, because of their large focal fault area and dislocation amplitude, that is, the focal body is very large, and also has the characteristics of group occurrence.

In the 40 years from 1837 to 1877, there were five earthquakes with magnitude 9 and above, followed by 75 years interval. In 1952-1964, there were four giant earthquakes, and then another 40 years later. In 2004, Sumatra, Indonesia, an earthquake with M = 9.3 occurred in Sumatra, Indonesia, and a m = 9 earthquake occurred in Japan on March 11, 2011.

Magnitude is a measure of earthquake strength, which is a classification of the magnitude of energy released by the source.

The unit is' Richter ', which is usually represented by the letter m. It is related to the energy released by an earthquake.

The greater the energy released, the greater the magnitude of the earthquake. For every magnitude difference of 1.0, the energy difference is about 32 times; for every 2.0 magnitude difference, the energy difference is about 1000 times.

In other words, an earthquake with magnitude 6 is equivalent to 32 earthquakes with magnitude 5, while an earthquake with magnitude 7 is equivalent to 1000 earthquakes with magnitude 5.

Do all the big earthquakes cause tsunamis?

Not necessarily. Academician Chen told reporters that the tsunami caused by the earthquake must meet three conditions: deep water, large earthquake and coastal topography from deep to shallow.

The tsunami disaster caused by several major earthquakes in Japan, most of which came from the Pacific side. For example, the famous Meiji tsunami (1896) and the Zhaohe tsunami (1993)

Darwin also recorded the tsunami caused by the great earthquake in Chile in 1835 in his exploration diary. He said with emotion: "the achievements made by countless human time and labor were destroyed in only one minute. '

Tsunami is coming. What should we do?

The earliest signal of earthquake and tsunami is strong ground vibration. There is a time difference between the arrival of earthquake wave and tsunami, which is just conducive to people's prevention.

If you feel strong vibration, don't get close to the seashore or the estuary of rivers.

If you hear reports of earthquakes nearby, pay attention to TV and radio news and be prepared for tsunami prevention.

Tsunamis sometimes reach thousands of meters away from the source a few hours after an earthquake.

If it is found that the tide suddenly abnormal fluctuation, the sea level drops significantly or there are huge waves, they should withdraw from the shore as quickly as possible.

China's offshore areas, such as the Bohai Sea, the Yellow Sea and the East China Sea, have an average depth of about 20 meters, 40 meters and 340 meters, respectively. They are not deep enough. Only the South China Sea has an average depth of 1200 meters. Therefore, the possibility of local tsunamis caused by earthquakes in most of China's sea areas is relatively small, and only in some places in the South China Sea and the East China Sea can a tsunami be generated. "Said academician Chen.

But we should not neglect to guard against it because the possibility is small.

China is located between the circum Pacific seismic belt and the Eurasian seismic belt, which are the two largest earthquake concentrated areas in the world.

China is a country with many earthquakes in the world, and also one of the countries suffering from the most serious earthquake disasters.

Indonesia earthquake tsunami disaster is so serious, in addition to the disaster itself destructive, lack of tsunami prevention, public awareness of disaster is also an important reason for the huge disaster. Therefore, mastering more disaster prevention knowledge at ordinary times can save fresh lives at critical moments.

China prepared to meet the challenge of one belt, one road, one in every act and every move. Ding Zhifeng said that China Earthquake Administration is currently working with ASEAN countries to promote the implementation of the China ASEAN Tsunami Monitoring and early warning system. Meanwhile, China has built more than 40 seismic stations along the "one belt" road, Pakistan and Algeria.

Academician Chen said that there are three main ways to reduce tsunami disaster: prediction of tsunami disaster, early warning and striving to minimize disaster after disaster.

Experts agree that only by carrying out regular publicity and education on disaster prevention knowledge, improving the public's scientific literacy of disaster prevention and enhancing the awareness of disaster prevention and mitigation can we effectively prevent disaster risks.