After the earthquake, due to the destruction of the surface and mountains, it may cause a variety of geological disasters. These types of disasters include: collapse, landslides, ground fissures, ground collapse, and sand liquefaction. These disasters may be derived from other disasters. For example, a large amount of loose rock soil caused by collapse and landslide may lead to debris flow; the ground fissure may develop into a collapse landslide; the landslide blocks the dammed lake formed by the river, which may cause disasters to the upstream and downstream. The unstable broken mountain body and the collapsed and slipped pile body are in danger of falling again and so on. Because they are not geological disasters directly generated by seismic waves, they are called secondary geological disasters.
2. How to identify geological secondary geological disasters?
Collapse
Also known as caving, collapse, and landslides, it is a geological phenomenon in which large rocks and clods are separated from the mother by gravity, dumped, collapsed, and rolled down to produce cuttings and debris.
Before the occurrence, it is generally seen that the cracks in the collapse gradually enlarge. There are often stones or clods falling, small collapses and small collapses occur, new cracks appear on the top of the slope, smelling abnormal smells, and tearing friction of rocks is heard from time to time. Wrong sound, abnormalities such as heat, helium, groundwater quality, and water volume.
Landslide
It refers to the process of sliding the soil layer or rock layer as a whole or scattered down the slope under the influence of rainfall, earthquake or artificial factors. It is also called “land slideâ€, “walking mountainâ€, “crossing the mountain†and “mountain peelingâ€.
Landslides are generally caused by long-term large-scale rainfall, cracks on the slopes; loose or bulging at the foot of the slope; subsidence in the upper part of the slope; deformation of the building on the slope. The water pipe is broken; the water in the spring water is abnormally changed; the underground sounds abnormally; the various signs are mutually confirmed.
3. Debris flow
It refers to the relatively viscous torrent formed by heavy debris, such as heavy rain, a large amount of ice and snow, and a large amount of rapid water flow in the mountain valleys. It is called "Dragonfly", "Blisters" and "Walking".
The precursors of the debris flow are also obvious. Generally, there are long-term large-scale rainfall. In rivers, the river surface is widened and the water flow is accelerated. The river becomes turbid water flow mixed with a large amount of firewood and branches; or the river suddenly stops flowing. It may be that there is a landslide upstream into the river valley, temporarily blocking the river to form a barrier lake.
When the valley occurred, there was a huge and continuous roar, which was obviously different from the sounds of locomotives, wind and rain, lightning, blasting, etc. It was a mixture of stones, trees and huge waters. The sky will become dim and the ground will be slightly shaken.
4. Ground collapse
It refers to the ground in karst areas and mine development areas. While a large amount of groundwater is extracted, underground killings are taken away in large quantities, causing the surface rock layers and soil layers to fall down. A geological phenomenon that forms a collapse pit (hole). Sudden.
5. Ground fissure
It is the abbreviation of ground crack, which is caused by natural factors (crust activity, water action, etc.) or human factors (pumping, irrigation, excavation, etc.) under the action of natural factors (crust, irrigation, excavation, etc.), and forms a certain length and width on the ground. A macroscopic surface damage phenomenon of cracks. Sometimes the ground fissure activity is related to seismic activity, or it is one of the earthquake precursor phenomena, or the residual deformation of the earthquake on the ground.
6. Stable Lake
It refers to a lake where landslides, earth-rock flows or lava block river valleys or riverbeds, and water is formed to a certain extent. It is usually caused by natural causes such as earthquakes, windstorms, volcanic eruptions, etc. When the lake is scoured, eroded, dissolved, and collapsed. When it is used, there will be an “overflowing dam†in the dammed lake. Eventually, because the dammed lake structure is in a very poor geological condition, the “breaking dyke†will evolve and the flooding of the flash flood will occur instantaneously, which will have devastating damage to the downstream area.
7. Regional sand liquefaction caused by earthquake
Due to the earthquake or other external forces, the saturated sand is subjected to strong vibration and loses its shear strength. It is in a flowing state and has no bearing capacity, causing the foundation to fail and destroying the building. This process and phenomenon is called sand liquefaction. The large scale and wide range of sand liquefaction caused by the earthquake will cause great damage to the engineering buildings.
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