Science and technology dynamics
We know that if we give a disturbance to the air, the sound will also be transmitted like waves through the form of waves. This is the sound wave. The sound that we usually hear is the sound waves coming into the ear to stimulate the tympanic membrane. The frequency range of sound waves can be divided into three frequency bands. The first is sound waves. This is the sound band that most people can hear. The frequency is between 20-16000Hz. The second is the infrasonic wave. People can't hear this band, 0.0001-20Hz. The third is the ultrasonic: 16000-10 of the 12th power of Hz, which is not heard by human ears, but many animals can hear it. Therefore, before the earthquake, the abnormal behavior of animals was one of the signs of the earthquake. So, can people also use infrasound for seismic detection?
In 2013, after the 4.20 Lushan earthquake, the digital infrasound monitor independently developed by the landslide research team led by Professor Xu Qiang of the â€œChangjiang Scholarâ€ of Chengdu University of Technology unexpectedly captured the Lushan earthquake during the early testing on the 20th. Infrasound signal. After analysis, it was found that the time that the infrasound wave generated by this earthquake reached the school was 08:02:52, which was about 6 seconds later than the start time of the main shock reported by the earthquake department. However, this is also the analysis of the infrasound wave after the earthquake. There is no great effect on earthquake prevention. Human beings can predict earthquakes through infrasound detectors. At present, there is no successful experience.
First, the propagation of infrasound waves in solids, in addition to longitudinal waves that can exist in air and water, also has transverse waves. When the subsonic wave signal from the source deep in the stratum propagates to the surface of the stratum far away, most of the energy is absorbed by the solid medium, and the remaining weak energy signal is submerged by the environmental infrasound signal. In order to obtain a subtle seismic source infrasound signal in the depths of the strata, it is best to place the infrasound monitoring instrument at depths as deep as possible within 8 to 10 km below sea level.
Secondly, nature has many subsonic sources, such as thunderstorms, storms, tsunamis, meteors, rock falls, waterfall torrents, ice cracks, avalanches, landslides, mudslides, etc. The vibrations of all objects can produce subsonic waves. In the production and life of mankind, mankind keeps producing infrasound waves. For example: blasting, building collapse, mechanical friction vibration, machine operation, etc. These infrasound waves have a great influence on the detection of infrasound signals released deep within the formation. How can we exclude the interference of natural and artificial infrasound waves on the surface of the Earth to ensure that the detection instrument can accurately capture the infrasound signal released in the deep stratum of the stratum and the initial stage of energy accumulation. This requires the further development of environmental noise silence and technical shielding techniques.
However, with the rapid development of science and technology, it is believed that one day, the detection and prediction of earthquake disasters using infrasound will become a reality. (Author: tadpole Jun)
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