What caused the Tangshan earthquake?

Earthquake is the vibration of the earth's surface caused by the sudden release of slowly accumulated energy in the earth. When the huge pressure on the earth's crust caused by the energy accumulated in the internal movement of the earth exceeds the limit that the rock stratum can bear, the rock stratum will suddenly break or dislocate, so that the accumulated energy will be released sharply and spread in all directions in the form of seismic waves, and an earthquake will be formed. A series of smaller aftershocks often occur after a strong earthquake.

Earthquakes are divided into natural earthquakes and artificial earthquakes. Natural earthquakes are mainly tectonic earthquakes, which are caused by the fracture and dislocation of rocks in the deep underground, so that the long-term accumulated energy is suddenly released and spread outward in the form of seismic waves, causing house shaking and ground vibration. Tectonic earthquakes account for more than 90% of the total number of earthquakes. Followed by earthquakes caused by volcanic eruptions, known as volcanic earthquakes, accounting for about 7% of the total number of earthquakes. In addition, earthquakes will also occur in some special circumstances, such as cave collapse (collapse earthquake) and large meteorites hitting the ground (meteorite impact earthquake).

Artificial earthquakes are earthquakes caused by human activities. Such as vibration caused by industrial blasting and underground nuclear explosion; High-pressure water injection in deep wells and water storage in large reservoirs increase the pressure on the earth's crust and sometimes induce earthquakes. (

1. What is the internal structure of the earth?

The interior of the earth can be divided into three layers: crust, mantle and core.

2. What is an earthquake?

A: The sudden release of slowly accumulated energy in the earth or the vibration of the earth's surface caused by human factors are called earthquakes.

3. What is a seismic source?

A place in the earth where earthquakes occur.

4. What is the epicenter? What is epicentral distance?

A: The projection point of the source on the ground is called the epicenter. The distance from the epicenter to any point on the ground is called epicentral distance.

5. What is the focal depth? What are shallow earthquakes, deep earthquakes and moderate earthquakes?

A: The vertical distance from the epicenter to the source is called the focal depth.

The focal depth of shallow earthquakes is less than 70km, the focal depth of deep earthquakes is more than 300km, and those with focal depth of 70-300km are moderate earthquakes.

6. How deep is the earthquake with the deepest focal depth in the world? Where are many deep earthquakes?

A: The earthquake east of Sulawesi, Indonesia1June 9, 934, with a focal depth of 720 kilometers.

Deep-focus earthquakes are most common in deep trenches around the Pacific Ocean, with deep-focus earthquakes in the northeast of China and moderate-deep earthquakes in the waters east of Taiwan Province Province.

7. According to the causes of earthquakes, they can be divided into several types.

Natural earthquakes and artificial earthquakes.

Natural earthquakes include tectonic earthquakes, volcanic earthquakes and collapse earthquakes. Artificial earthquakes include vibrations caused by underground nuclear explosions and earthquakes caused by reservoir impoundment.

8. What is a tectonic earthquake? What are the characteristics?

Tectonic earthquake is a natural earthquake caused by rock fracture caused by tectonic movement in the earth, which is closely related to geological tectonic system and mostly distributed in the crust 5-30 kilometers underground. It is characterized by long duration, wide range of influence, strong destructive power and repetitiveness. Tectonic earthquakes account for more than 90% of global earthquakes.

9. What is a volcanic earthquake?

The natural earthquake caused by volcanic eruption has a short duration, a small influence range and a focal depth of less than 10 km.

10. What is a collapse earthquake?

The top of the underground cave formed by natural causes can't support the earthquake caused by rock collapse.

1 1. What are near earthquakes, near earthquakes and far earthquakes?

The epicentral distance is less than 100 km, which is a local earthquake; The epicentral distance1000 km-1000 km is a near earthquake; The epicentral distance is greater than 1000 km, which is a teleseism.

12. The magnitude is the scale. What are sensible earthquakes, destructive earthquakes, major earthquakes and minor earthquakes?

Small earthquakes with magnitude less than 3, sensible earthquakes with magnitude above 3, destructive earthquakes with magnitude above 5, and large earthquakes with magnitude above 7.

What is the order of magnitude?

Magnitude refers to the magnitude of the earthquake itself, which is related to the energy released by the source. The greater the energy, the greater the magnitude, and the earthquake has only one magnitude. The magnitude difference is one level and the energy difference is 33 times.

What is the earthquake intensity? What are the factors that affect the earthquake intensity?

The degree of influence and destruction of an earthquake on a certain area is called intensity. Generally speaking, the greater the magnitude, the greater the intensity. The epicentral distance of the same earthquake is different with different intensities. Besides the magnitude and epicentral distance, the factors that affect the intensity are also related to the address structure and the seismic performance of the ground buildings.

15. What is the criterion for judging each intensity indicated in the China Earthquake Intensity Table?

What is seismic wave?

Seismic wave is an elastic wave generated inside the earth when an earthquake occurs, and it is a way to release energy from an earthquake.

17. What kind of seismic waves? What are the characteristics?

Seismic waves include body waves and surface waves, and body waves are divided into longitudinal waves and shear waves.

The vibration direction of the shear wave is perpendicular to the advancing direction of the wave, while on the ground, the vibration direction of the longitudinal wave is consistent with the propagation direction, reflecting the vibration of the ground jumping up and down (jumping and lifting). Compared with the two, longitudinal waves travel faster than shear waves, so after an earthquake, you feel like jumping up and down, followed by shaking from side to side. In addition, the amplitude of shear wave is larger than that of longitudinal wave, which is destructive. The horizontal rocking force of shear wave is the main cause of building damage.

18. What's the difference between magnitude and intensity?

The magnitude reflects the magnitude of the earthquake itself, which is only related to the earthquake release ability, while the intensity reflects the impact and damage to the ground. An earthquake has only one magnitude, but its intensity varies from place to place. The intensity is not only related to the magnitude, but also to the focal depth, the distance from the epicenter and the conditions under which seismic waves pass through the medium.

19. How many earthquakes have occurred on the earth in a year, and how many destructive earthquakes are there?

There are more than 5 million earthquakes in the world every year, including destructive earthquakes 1000, and more than a dozen major earthquakes of magnitude 7 or above.

20. Where are there many earthquakes in the world?

Earthquakes in the world are mainly concentrated in the following two areas:

(1) Pacific Rim Seismic Belt: It includes the Pacific coast of North and South America, Aleutian Islands and kamchatka peninsula, passes through Thousand Islands and Japanese Islands, passes through Taiwan Province Province of China to the south, and then turns to the Philippines to reach New Zealand to the southeast.

(2) Himalayan-Mediterranean seismic belt: from western Indonesia through Myanmar to Hengduan Mountains and Himalayas in China, across Pamirs, and through Central Asia to the Mediterranean Sea and its coast.

2 1. How deep did the seismic belt originate?

The focal points of most earthquakes in the world are mostly distributed in areas 5-30 kilometers underground.

22. What is the biggest earthquake in the world?

At present, the largest earthquake recorded has not exceeded M = 8.9, namely, the M = 8.9 earthquake in Chile, South America on May 22nd 1906, 65438+1October 3rd1,the offshore near the Ecuador-Colombia border in South America, and the sea east of Japan's Sanlu on March 2nd 1933.

23. How many major earthquakes of magnitude 8 or above have occurred in China? Give three examples.

China is a country with many earthquakes. According to the existing statistics, there were 8+earthquakes 17 times, 1679, and an 8+earthquake occurred in Sanhe, Hebei Province in September. 1920 65438+an earthquake of magnitude 8.5 occurred in Haiyuan in February; 1927 An earthquake of magnitude 8 occurred in Gulang, Gansu Province in May; An earthquake of magnitude 8.5 occurred in Chayu, Tibet in August, 1950, 10, and an earthquake of magnitude 8.5 occurred in the sea area east of Taiwan Province Province in October, 1972.

24. There have been several earthquakes of magnitude 7 or above in our province, and four cases have been cited.

* * * happened five times. Sanhe 1679 M8 earthquake; 1830 an earthquake of magnitude 7.5 occurred in Cixian; 1966 Xingtai m 7.2 earthquake; 1976 Tangshan earthquake with magnitude 7.8; 1976 Luanxian 7. 1 earthquake.

25. What are the major earthquakes in China?

The main earthquakes in eastern China are Tanlu seismic belt, Hebei plain seismic belt, Wei Fen seismic belt, Yanshan Bohai seismic belt and southeast coastal seismic belt. There are North Tianshan seismic belt, South Tianshan seismic belt, Qilian seismic belt, Kunlun seismic belt and Himalayan seismic belt in the west. The central part is the North-South seismic belt, which runs through China. There is also the Taiwan Province seismic belt, which is a part of the western Pacific seismic belt.

26. What seismic zones are there in North China?

The earthquake zone is a strong earthquake zone with frequent earthquakes. Earthquakes in North China include Hebei Plain seismic belt, Wei Fen seismic belt, Yanshan-Bohai seismic belt and Lujiang seismic belt. According to geomechanics, China can be roughly divided into 20 seismic zones.

1. Taiwan Province province belt; 2. Coastal areas of Fujian and Guangdong; 3. Northeast deep seismic belt; 4. Yingkou-Tancheng-Lujiang belt; 5. Hebei plain belt; 6. Haiyuan-Songpan-Ya 'an Belt; 7. Shanxi belt; 8. Weihe Plain Belt; 9. Yinchuan Belt; 10. Lanzhou-Tianshui belt; 1 1. Hexi Corridor; 12. Mabian-Qiaojia-Copper Kelp; 13. Mianning-Xichang-Yufu Belt; 14. Tengchong-Lancang River belt; 15. Ailao mountain belt; 16. Luhuo-Ganning belt; 17. Huashixia belt; 18. Lhasa-chayu belt; 19. western Tibet; 20. Tianshan belt.

27. Who invented the first seismograph in the world? Brief introduction of seismograph development?

The first seismograph in the world was invented by China scientist Zhang Heng in BC 132. It is called the seismograph after the wind.

The modern seismograph was built in the 1990s of 18, and its principle is basically similar to that of the seismograph after the wind. Seismographs have developed rapidly, including long period and short period, and have realized wireless telemetry, magnetic tape recording and digitization. The sensitivity ranges from several times to several thousand times, tens of thousands of times, hundreds of thousands of times or even millions of times, and the period ranges from 0.05 second to 100 second.

28. What is earthquake prediction? How many kinds are there?

Earthquake prediction is the prediction of the time, place, magnitude and impact of destructive earthquakes in the future, which can be divided into long-term prediction, medium-term prediction, short-term prediction and imminent earthquake prediction.

29. What is the content of long-term earthquake prediction?

Long-term earthquake prediction refers to the prediction of earthquake risk and its influence in a few years to decades or longer. Including national or regional seismic zoning; Construction planning and project site seismic intensity, ground motion parameters, seismic zoning and earthquake damage prediction; National or regional seismic activity trend prediction.

30. What are the mid-term, short-term and impending earthquake predictions?

Medium-term earthquake prediction refers to the prediction of the time, place and magnitude of destructive earthquakes in several months to several years;

Short-term earthquake prediction refers to the prediction of the time, place and magnitude of destructive earthquakes in a few days to several months;

Impending earthquake prediction refers to the prediction or warning of a destructive earthquake in a few days;

3 1. How many earthquakes were successfully predicted in China?

Two earthquakes on March 23rd and 24th in Wuqia County, Xinjiang have been successfully predicted, 197 1. 1February 4, 975 Haicheng, Liaoning, earthquake with magnitude 7.3; 1Longling earthquake with M = 7.5 in Luxi, Yunnan on May 29th, 976,1Songpan earthquake with M = 7.3 in Sichuan on August 6th, 976. In particular, the Haicheng earthquake of magnitude 7.3 was recognized all over the world and won the second prize of national scientific and technological progress. On July 1995, an earthquake of magnitude 7.3 occurred in Menglian, Yunnan. On July 1 1, the Seismological Bureau of Yunnan Province reported to the local county cadre meeting and asked the local government to take measures, which greatly reduced the losses and was commended by the Yunnan Provincial Government and the State Seismological Bureau.

32. The laws and regulations on earthquake prediction in China were approved by leaders at which level, when was it approved, and when was it promulgated by the State Seismological Bureau?

1approved by the State Council on June 7th, 988,1released by the State Seismological Bureau on August 9th, 988.

33. What is the significance of China earthquake prediction laws and regulations?

In order to strengthen the management of earthquake prediction and ensure the safety of people's lives and property and the smooth progress of national economic construction.

35. Is there a precursor to the earthquake?

Yes Under the action of in-situ stress, in the process of stress and strain gradually accumulating and strengthening, rock mass will cause a series of abnormal changes in physics, chemistry, biology and meteorology of the source and nearby materials. We call these abnormal changes related to earthquake preparation and occurrence as earthquake precursors. Since Xingtai 1966 earthquake, China has recorded 1000 precursory anomalies before 70 moderate earthquakes.

36. What are the types of earthquake precursor anomalies?

It can be divided into 10 categories, namely: earthquake precursors, crustal deformation, gravity, geomagnetism, geoelectricity, hydrogeochemistry, dynamics of underground fluids (water vapor, gas and oil), stress, strain, meteorological anomalies and macroscopic precursor anomalies.