Why is the mechanism of the Afghanistan earthquake expanding?

The earthquake that struck eastern Afghanistan on the 22nd has killed more than 1,000 people so far, and rescue teams are continuing search activities, but the activities are difficult due to the lack of roads leading to the site. ..

Under these circumstances, UN agencies and the neighboring government of Pakistan are in full swing for relief activities.

In Afghanistan, a magnitude 5.9 earthquake struck in the eastern host state before 6 am on the 22nd of Japan time.

Local officials told NHK that so far more than 1,000 people have been killed and more than 1,600 injured in the host state and neighboring Paktika.

In the affected areas, many houses were piled up with sun-dried bricks, and it is believed that many people are still trapped under the collapsed houses.

Search activities by rescue teams are continuing at the site, but the activities are difficult due to the lack of roads leading to the site.

Under these circumstances, the United Nations WFP = World Food Program carried out work on the 23rd to load flour to be sent to the disaster area in the capital Kabul.

A total of 130 tons including flour provided by the Japanese government will be sent.

"The important thing is to get emergency supplies to those in need as soon as possible," said Sherry Tucklar, a spokeswoman for the WFP Afghanistan office. People in Afghanistan are patient but suffering. Don't forget, "he appealed for support.

In addition, the neighboring Pakistani government has also started full-scale relief activities from the capital Islamabad by launching simple tents and trucks loaded with medicines toward the affected areas.

In Afghanistan, since the Islamist Taliban regained power in August last year, embassies in each country have closed and support groups such as international NGOs have withdrawn, so prompt support can be provided. It is an issue.

Why is it so damaging?

We will explain based on the views of experts who are familiar with local earthquakes and buildings.

Earthquake caused by plate collision

Professor Hiroyuki Tsutsumi of Doshisha University, who is familiar with local seismic activity, says that the movement of the plate is greatly related to this earthquake.

In Central Asia, a bedrock called the "Indian Plate" moves north at a speed of about 4 cm per year and collides with the "Eurasian Plate".

This raised the Himalayas, also known as the "roof of the world."

The collision between the plates also exerts force on the eastern and western sides of the Himalayas, causing strain to build up.

Afghanistan and Pakistan located on the west side have the "Chaman Fault" extending from north to south, and there were magnitude 7 class earthquakes in 1505, 1892, and 1935, and small active faults in the vicinity. It means that it is distributed in large numbers.

In this area, there are many types of earthquakes in which the fault moves to the left according to the movement of the plate, and the epicenter this time is a hundred and several tens of kilometers east, but it is thought to be the same mechanism.

Professor Tsutsumi said, "The magnitude of the earthquake is not so large, but since the epicenter was a shallow, direct-type earthquake, I think we were hit by strong tremors around the epicenter. There is a possibility that an earthquake of the same magnitude will occur in the future. , It is necessary to proceed with relief activities while paying close attention to the transition of seismic activity in the field. "

Large earthquakes occur one after another in the east and west of the Himalayas

In the western part of the Himalayas, where the Indian Plate and the Eurasian Plate collide, large-scale earthquakes have been repeated and severe damage has occurred frequently.

According to a summary by the Meteorological Agency and the Cabinet Office, a

magnitude 7.6 earthquake struck the Kashmir region in northeastern Pakistan in October 2005, killing approximately 75,000 people in Pakistan, India, and Afghanistan.

▽ In October 2015, a magnitude 7.5 earthquake with an epicenter in northeastern Afghanistan killed more than 300 people in Afghanistan and Pakistan in total.

In addition, there was a major earthquake approaching magnitude 8 on the eastern and southern sides of the Himalayas, killing more than 87,000 people and the May 2008 Sichuan earthquake in China, which killed about 9,000 people. There was a big earthquake in Nepal in April 2015.

The effects of plate collisions are widespread around Central Asia, resulting in repeated earthquake damage.

"Adobe" housing with low earthquake resistance and easy spread of damage

Why did the Afghanistan earthquake, which killed more than 1,000 people, spread?

Fumio Yamazaki, a senior researcher at the Institute for Disaster Prevention Science and Technology, who has surveyed the site near the border of neighboring Pakistan, said, "Most of the local houses have a structure called" Adobe ", which is a stack of sun-dried bricks and mortar, and is earthquake-resistant. It is thought that it led to great damage because of its low sex. "

Senior Researcher Yamazaki conducted a field survey near the border of Pakistan, which was severely damaged when the magnitude 6.8 earthquake struck Afghanistan in 1991.

Regarding the impression of this damage, Senior Researcher Yamazaki said that he felt that the structure of the house had hardly changed from 30 years ago.

In Afghanistan and Pakistan, there are many houses built from soil and stone, and in particular, it is characterized by a building called "Adobe", which is a stack of sun-dried bricks and mortar.

Many of the houses are not reinforced with reinforcing bars, etc., and because of their low seismic resistance, even shaking with a seismic intensity of 5 or higher will cause them to collapse significantly, causing human damage.

Regarding the cause of the spread of damage, Senior Researcher Yamazaki said, "It is thought that most people were sleeping because of the earthquake before dawn. Unlike Japanese houses, houses made of soil and stone lose their" living space "when they collapse. As a result, the damage will become more serious and rescue operations will be difficult. There is a possibility that there are cracks in the walls due to the shaking of the earthquake, and if it rains in the future, it may penetrate from there and lead to collapse. It is necessary to take measures such as covering it with a sheet to prevent water from entering. "

On the other hand, not only in Afghanistan but also in developing countries, there are many houses with bricks piled up, and he mentioned the tendency that the damage caused by the earthquake is likely to spread. There are few examples. It is necessary for international organizations to think about ways to provide support that is truly useful to the local people in the wake of this earthquake. "