Today in History|Mt. Tibet, the sixth most powerful earthquake in the 20th century

1950 August 15 (lunar month two days), Medog in Tibet, China's largest-ever earthquake. The Richter scale earthquake was 8.6 and 1526 people died. This is the sixth most powerful earthquake in the 20th century. It is caused by the edge collision of the polymerization plate. The last time was the Assam earthquake in 1897. The maximum intensity of the epicenter was 12 degrees. In the epicentral area, traffic was cut off after the earthquake. Medog County is located in the 10th district, and Chayu County is located in the 11th district. The houses in the extreme earthquake area were all leveled, mountains and rivers moved, terrain changed, and several peaks collapsed and blocked the Yarlung Zangbo River, and landslides pushed five villages into the river. This earthquake was more than 500 kilometers away from the Assam earthquake in India in 1897 . Historical statistics show that strong earthquakes along the southwestern border of China have a recurrence period of around 50 years to 70 years.

Earthquake loss

Medog's elevation is only 800-1200 meters , which is a piece of land and Tibetan means "flower." 1950 August 15 took place

A large earthquake that shook the entire Tibetan Plateau. The entire Brahmaputra River Bend and 27 counties such as Miling and Chaga and parts of Assam in India have been involved in this disaster.

Because of its special geology, geographical structure, and natural environment, the Yarlung Zangbo Grand Canyon area not only causes earthquakes but also breeds many kinds of animals and plants. This makes our investigation here not only unexpected but also unexpected. Everywhere is life-threatening.

secondary disaster

Seismic Hidden Pillar collapse and debris flow

The Medog Canyon area is an earthquake-prone area. During my visit to the Grand Canyon, I experienced two quakes in my personal experience. One of them woke me up from my sleep. According to the data I surveyed in Zhaqu in 1973 , it was estimated that around 1864 , a large-scale destructive earthquake occurred in the Grand Canyon.

The biggest feature left by this massive earthquake on the ground, and also a potential hazard in the future, are the collapsed rock piles and the debris flow on the two sides of the canyon. The piling stones resemble a dry stone river. The troughs filled with cuttings, gravel, and boulders are carved into the bedrock. They lie on the uphill mountain from the tall cliff top on the slope of the valley, and they have large scale. Hundreds of meters to thousands of meters. Once the cliffs at the source have collapsed or the bulging stress caused by earthquakes, heavy rain, and noon exposure, it may trigger sand grit slips in the valleys, and even produce a chain reaction that evolves into an overwhelming boulder torrent. When the riverbed collapsed into a river, there was a time when river flow was blocked.

The largest landslips and mudslides occurred near the village of Baobun in the lower part of the Grand Canyon. In the summer of 1973 , a rocky cliff in the village of Beibun collapsed in a rainstorm. The collapsed boulders pushed the mudstones in the downstream trenches into a tens of thousands of tons of mudslides and rushed towards the Yarlung Zangbo River, cutting off a runoff of 10,000 in one fell swoop. The flow of seconds in Limi River lasted for one day. On the second day, the river overflowed with embankments and formed a flood peak. It almost washed away the downstream liberation bridge.

We have been involved in many accidents through pours of rocks or mudslides. In order to investigate the catastrophic rock formations, I also climbed to the cliffs of the crisis along the rocks. The steep rock dump is a sloping stone slope. The debris stones on the slope are in the critical state of gravity. Every step must be taken. In 1973 , we had to cross a stone pile from Aspen to Dabo. This inverted stone pile is inserted from the top of the kilometer up to the bottom of the river, and it is five or sixty meters wide. The stone contains the debris and boulders mainly composed of gray sericite and quartzite. In order to prevent the concentration of weight, we took a sparse formation to advance. Unexpectedly, one of the people on the top stepped on its knees and smashed a stone to roll down from the old side. One of the small stones was lying on the back of Lao Zheng. When Lao Zheng evaded, I stepped on the debris of the foot and formed a rocky rain toward me. I hurried to catch a step behind a large rock, fortunately only a small stone hit my shoulder.

The collapsed rock dumps and mudslides continuously flooded the tributaries of the Yarlung Zangbo River with a large amount of silt, debris, and boulders, forming a hotbed of unusual solid runoff in the Big Gap. Paleoliths and mudslides can block waterways, fill storage capacity, and bury hydraulic structures and power facilities, which seriously restricts the development of the Grand Canyon water energy resources in the form of dams.

Earthquake impact

The earthquake has a large intensity, a shallow source, and a wide spread. Seismologists all over the world are stunned and all seismographs have been overpowered by powerful seismic waves. So that American scientists think that it happened in Japan, but Japan thinks it happened in the United States.

After the earthquake, traffic in the epicentral area was cut off. The houses in the extreme earthquake area were all leveled, mountains and rivers moved, terrain changed, and several peaks collapsed and blocked the Yarlung Zangbo River, and landslides pushed five villages into the river. In the Himalayas, hundreds of thousands of square kilometers of land are completely different, and the Yarlung Zangbo River is cut into four sections.

The information in this article comes from the Internet and was reorganized and edited by China Rescue Equipment Network.