House shaking is not necessarily a precursor to earthquakes. According to building standards, 150-meter-high buildings allow a swing amplitude of 25 cm at the top, and the world's tallest building 828-meter-high Dubai Burj Khalifa , which allows a swing amplitude of 3 meters at the top when designing. High-rise residents may feel a slight shaking during a typhoon, which meets building standards, but most of the time the human body cannot feel the shaking of the tall buildings.
If the chandeliers and hanging items in the house shake significantly, it can basically be determined that it is the impact of the earthquake. Earthquakes occur more than 500,000 times a year around the world, and most earthquakes occur in the oceans and sparsely populated lands. Most earthquakes are earthquakes that do not feel the sensation or earthquakes that do not threaten people. Earthquakes that can truly threaten humans occur 10 to 15 times a year around the world.
When an earthquake hits, the weaker longitudinal wave first reaches the ground. The longitudinal wave can cause the building to vibrate up and down. After 10 seconds, the powerful transverse wave reaches the ground. The building begins to shake violently from side to side. Humans have only 10 seconds to prepare for resistance.
wants to make predictions before an earthquake occurs, but science and technology cannot do it now.
Many signs of earthquakes are rumors, such as earthquake cloud . The Meteorological Bureau has denied the rumors more than once that this kind of long cloud is formed by high-rise air convection and has nothing to do with earthquakes. Many folk scientists try to explain from various angles, such as electromagnetic theory, which believes that the crust is squeezed under stress before the earthquake, which affects the distribution of the magnetic field, changes the water vapor and dust concentration of ionosphere , and further affects the cloud arrangement of troposphere . There are also heat theory and radiation theory. At first glance, it seems quite professional, but in fact there is no scientific basis, because various precision instruments have been deployed from the surface to space to monitor water vapor, sound waves, radiation, heat, etc. in real time. Various data have been included in the monitoring and analysis, and there is no so-called "seismic cloud" at all.
On February 17, 2016, strip clouds appeared in Wuyuan , Jiangxi, but no threatening earthquake occurred in the country during this period.
On July 28, 2017, strip clouds appeared in Changchun , Jilin, but no threatening earthquake occurred in the country during this period.
Is there no sign of earthquake? There may be signs of an upcoming earthquake.
It is recorded that in 373 BC, before the earthquake in Helis City in Greece, mice fled one after another, snakes also ran out of the city. The abnormal behavior of animals also included fish jumping out of the water, dogs barking, and bees not returning to their nests. From a scientific point of view, it is because animals can sense infrasound wave below 10 Hz that humans cannot hear. This infrasound wave is generated by the squeeze between lithosphere inside the earth. It resonates with the internal organs of animals and can cause discomfort in animals, but infrasound waves are rarely generated and does not mean that earthquakes will definitely occur.
Another situation is an ocean earthquake. When the tsunami of Indian Ocean was about to occur in 2004, a little girl saw many bubbles appearing on the sea surface and the sea water receded. The little girl immediately thought of the tsunami knowledge in class and immediately told her mother that she saved more than 100 lives. This tsunami was formed by earthquakes caused by the squeezing and fracture of the Asian and European plates of Indian Ocean plates, but in most cases, marine earthquakes do not necessarily cause tsunamis, so there are not necessarily precursors.
The reason why earthquakes are difficult to predict is not only technical reasons, but the high prediction cost is also a difficult problem. If the Earthquake Bureau announces that a 5% chance of a major earthquake in the next 3 days, the normal reaction of a person is definitely to leave City A immediately no matter how small the probability is, which will cause panic and the entire social order will be disrupted.
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