Natural disasters in Mianyang
The main geological structural disasters in Mianyang are as follows:
1. Earthquake: Mianyang City is located in the western mountain area, namely Pingwu, Beichuan and Anxian mountains, and the Northwest Mountainous Area of Jiangyou, which is one of the earthquake prone areas in Sichuan Province. The Longmenshan seismic belt passes through Anxian, Jiangyou and the area to the north, and the Songpan Maowen seismic belt passes through Pingwu and Beichuan. The area threatened by earthquake accounts for more than 86% of the total area.
2. Collapse: Urban collapse mainly occurs in the Northwest Mountainous steep slope. The mountain slope in the northwest of the city is steep, and the area proportion of steep slope above 25 degrees in Pingwu County and Beichuan county is the largest. The Silurian Maoxian group in Pingwu and Beichuan counties is composed of a set of thick phyllite intercalated with crystalline limestone. The lithology is very broken and the distribution area is wide. Therefore, it is easy to form collapse, landslide and debris flow under the action of gravity, rainstorm and earthquake. In 1976, the Songpan and Pingwu earthquakes occurred in hujiamo area of Baima commune. Along with the earthquake, a large number of rocks collapsed. After the collapse, the mountain top became a bald ridge. The collapsed rocks blocked several rivers and formed several small lakes. The above collapses also occurred in Beichuan, Jiangyou and Anxian mountain areas.
3. Landslide: due to the steep slope and broken rock in the Northwest Mountain Area of the city, the landslide is very easy to occur under the action of earthquake and rainstorm. After the Songpan and Pingwu earthquakes in 1976, landslides, sliding surfaces and landslide walls can be seen in Wanglang Nature Reserve. The trees on the landslide mass are crooked and disordered, forming "drunken Hanlin", and a large number of trees are buried in the lower part.
4. Debris flow: debris flow in the city is mainly distributed in Northwest Mountainous areas such as Pingwu, Beichuan and other places. Besides rainstorm, earthquake is often an important cause. Debris flow often occurs in brittle or rigid rock, fracture developed and easily broken zone, often forming steep terrain or cliff.