The U.S. Geological Survey has published statistics on the annual earthquakes. It was found that about once a year on earth-quake disaster happens, carrying away many lives. The strength of the earthquake reaches eight points or more. About two dozen earthquakes seven to seven and a half points. One hundred and twenty earthquakes — up to six and a half points. Eight — the power of up to five and a half points, more than six hundred earthquakes a year a force of about four and a half points, and finally, almost fifty thousand weak vibration force of just over three to three and a half points.
In addition to these statistics information center Geological Survey also identified a list of the most devastating earthquakes.
The first place in this list is a disaster, which occurred in the town of Xian of Shaanxi Province January 23, 1556. Only one figure — 830,000 casualties — speaks for itself. The earthquake occurred due to shifting tectonic plates, which in turn caused the collapse of the "walls" of narrow valleys. In an instant, the unsuspecting residents of Shensi, were buried alive deep underground, a job as a town, has ceased to exist. This disaster is described in detail in the historical annals of ancient China. Also in China in the twentieth century, 28 July 1976, in the city of Tangshan happened to the destructive force of a powerful earthquake that killed two hundred forty-two thousand lives. Propulsion was nearly eight points. According to the number of victims of this catastrophe is not far from Beijing ranks second in the list of geologists. Next on the list was named an earthquake off the coast of Sumatra. Propulsion reached nearly ten on the Richter scale.
The resulting tidal wave as tall as a four-story house was the cause of the death of one hundred and fifty thousand people. Affected people in India, Sri Lanka, Thailand, Indonesia and Malaysia. Concludes the list of the world's worst earthquake disaster in 1962 that took place in Alaska. Tremors were in force 9.2 Richter. This earthquake was among the ten greatest disasters of modern times.
Each year on Earth is about 50,000 earthquakes, sufficiently intense to be seen without the aid of instruments. Of these, about 100 are powerful enough to produce significant damage if their center will be located near population centers. Very large earthquakes occur on average once a year.
Minor earthquakes occur nearly constantly around the world in California and Alaska (USA), in Chile, Peru, Indonesia, Iran, in the Azores, Portugal, New Zealand, Greece and Japan. Large earthquakes occur less frequently. About ten times more earthquakes, big 4, there is a certain time period than earthquakes larger than 5. For example, in the UK (low seismicity), it was calculated that the average recurrence:
— earthquake of 3.7 — 4.6 every year
— earthquake of 4.7 — 5.5 every 10 years
— earthquake of 5.6 or larger every 100 years.
The number of seismic stations has increased from 350 in 1931 to many thousands today. As a result of the greater number of earthquakes with advanced reporting tools. The U.S. Geological Survey provides data that in 1900 had an average of 18 large earthquakes (magnitude 7.0-7.9) and one great earthquake (magnitude 8.0 or greater) per year, and that this average has been relatively stable.