Weather Precursors of Tangshan Earthquake

1. Macroscopic precursors of earthquakes

People's senses can directly perceive earthquake precursors, which are called macro precursors of earthquakes. The more common ones are the sudden rise and fall of well water, discoloration and odor, flowering and bubbling, temperature fluctuation, sudden change of spring water flow, sudden change of hot spring water temperature, abnormal animal habits, earth sound and earth light before the earthquake, etc.

Macroscopic precursors play an important role in earthquake prediction. Before Liaoning 1975 Haicheng earthquake with M = 7.3 and 1976 Songpan-Pingwu earthquake with M = 7.2, seismologists and the general public had observed a large number of macroscopic anomalies, which provided important information for the successful prediction of these two earthquakes. However, we should also pay attention to the various macro phenomena listed above, which may be caused by various reasons, and are not necessarily signs of earthquakes. For example; The group fluctuation of well water and spring water may be related to rainfall, and may also be affected by nearby pumping, drainage and construction. The discoloration of well water may be caused by pollution, and the abnormal behavior of animals may be related to weather changes, diseases, estrus and external stimuli. Also be careful not to mistake welding arc light and lightning for earth light, thunder for earth sound, and fireworks and flares for underground fireballs.

-once you find an abnormal natural phenomenon, don't easily draw the conclusion that an earthquake will happen soon, let alone panic. Instead, it is necessary to find out the time, place and relevant situation of abnormal phenomena, protect the site, report to the earthquake department or the government, and let the professionals in the earthquake department investigate and verify the truth.

2. Microscopic precursors of earthquakes

Earthquake precursors that can't be detected by human senses and can only be measured by special instruments are called earthquake microscopic precursors, which mainly include the following categories:

Abnormal seismic activity. There is a certain relationship between large and small earthquakes. Although there are not many major earthquakes, there are many small and medium-sized earthquakes. Study the characteristics of moderate and small earthquakes. It is possible to help people predict the occurrence of future major earthquakes.

Terrain anomaly. Before the earthquake, the crust near the epicenter may be slightly deformed, and the rocks on both sides of some faults may be slightly displaced. With the help of precision instruments, this very small change can be measured, and analyzing these data can help people predict the occurrence of future major earthquakes.

Geophysical changes. In the process of earthquake preparation, some changes may occur in the physical properties of rocks in the source area and its surrounding areas. Using precision instruments to measure the changes of gravity, geoelectricity and geomagnetism in different areas can also help people predict earthquakes.

Changes of underground fluid. Groundwater (well water, spring water, water contained underground), oil and natural gas and some other gases may be generated and stored in underground rock formations, which are all underground fluids. Measuring the chemical composition and some physical quantities of underground fluid with instruments and studying their changes can help people predict earthquakes.

3. Earthquake observation network

In order to capture the microscopic precursors of earthquakes, it is necessary to establish an earthquake observation network covering this area for long-term precise observation.

An instrument for recording earthquakes is called a seismograph. Stations specializing in earthquake observation are called seismographs or seismographs. As early as 1800 years ago, Zhang Heng, a famous scientist in China, invented the world's first seismograph-"Houfeng seismograph". Modern seismographs adopt the most advanced electronic technology with high sensitivity, and there are even special submarine seismographs and deep well (borehole) seismographs. At present, a considerable number of seismic stations can automatically record seismic signals without special observation, and automatically transmit the signals to the receiving center through cables or radio waves, and then the signals are automatically processed by computers. This is the so-called telemetering seismic network. Modern telemetering seismic network has been established in many areas of China, including Sichuan Province. In addition, there are earthquake precursor observation stations such as geoelectricity, geomagnetism, gravity, topographic change and underground fluid.

Before liberation, there was only one seismic station and three seismologists in old China, and the earthquake cause was extremely backward. After liberation, the cause of earthquake in New China has been improved. In 957, Chengdu Seismological Station, the first seismic station in Sichuan Province, was established in the western suburbs of Chengdu. 1966 After the Xingtai earthquake, with the cordial care of Premier Zhou Enlai, the earthquake cause in China accelerated. 197 1 year, the state seismological bureau (now seismological bureau of China) was established. After nearly 30 years of hard work, the earthquake observation network has begun to take shape. At present, more than I000 modern seismic stations (including local seismic stations) have been established in China, and seismic observation technology has been widely used.