'Concussion in Hanoi is related to Japan earthquake'

According to Dr. Nguyen Dinh Xuyen, former director of the Institute of Geophysics, the tremor in Hanoi on March 24 was the result of an impact chain after the magnitude 8.9 earthquake in Japan.

How do you rate the earthquake on March 24 in Myanmar?

This earthquake lies on the Burma - Yunnan (China) fault, which flows down the Lao-Thai border. This fracture is quite strong, can cause an earthquake of 7-7.5 magnitude. In comparison to the intensity, this earthquake is stronger than the most active fault of Vietnam (in Son La, Song Ma and Lai Chau regions), which can only cause magnitude 6.5-7 magnitude.

Repeatedly for several days, many countries and territories near Vietnam such as the Philippines, Taiwan and Myanmar experienced strong earthquakes. Can you explain this?

I think this is a consequence of the earthquake in Japan on March 11. This earthquake occurred after a process of energy accumulation when the North American plate moved under the Pacific Plate. The movement of the stratigraphic plate in this 8.9-magnitude earthquake has penetrated deep into the earth's crust. The collision can be likened to a punch, causing vibrations throughout the earth's crust.

The consequence of this collision has a stimulating effect on the energy accumulation process in some fault zones. The earthquake cycle in earthquake areas can therefore be accelerated several decades. So in Taiwan, the Philippines on March 20 happened a magnitude 5.9 earthquake and Myanmar was 6.8 richter on March 24. Maybe not without the earthquake in Japan, those earthquakes still happen, but not at this time.

In the next few months, moderate-sized earthquakes of 5 or more in magnitude can still occur with thick frequencies in many parts of the world.

According to Dr. Nguyen Dinh Xuyen, the terrible earthquake in Japan had an impact on these
fault zone, accelerating the earthquake cycle in these areas. Photo of two earthquakes in Japan
Ban and Myanmar: Googlemaps.

In the earthquake on March 24, the same is a high-rise building, why do some people in Hanoi do not feel?

- Hanoi in general has weak soil, except Soc Son. In particular, the inner city is in the form of ' Hanoi average ', which is weaker than other localities. In addition, the southern part of the city is in the ' very weak ' form. Therefore, during the earthquake in Myanmar on March 24, the most obvious area of ​​influence was Hoang Mai and Thanh Tri. I am in Long Bien and I do not see any reflection.

In general, if earthquakes occur somewhere affecting Vietnam, Hanoi will be affected more strongly than one level due to weak ground. According to my calculations, with the distance and intensity of the earthquake in Myanmar, tremors in Hanoi are level 4 (according to MSK-64 scale), plus minus 0.2 levels. Meanwhile, the same distance but in other localities only about level 3.

According to the Institute of Geophysics, Hanoi is located on the two Red River and Chay river faults which are identified as having the strongest earthquake of 6.5 Richter scale. If it happens, what is the impact level?

In 1285, a strong tremor of level 8 was caused by a 5.5-magnitude earthquake that broke the stone monument at Bao Thien pagoda. The cycle of an earthquake is so strong about 1,000 years. For some areas in Hanoi with soft ground, soil along the river, the mudflats, the maximum impact may reach level 9 (causing complete damage to the house; the ground may be cracked wide 10 cm).

If this possibility occurs, high-rise buildings that are located on that area are not designed to have adequate seismic resistance. Old houses may fall.

In fact, in recent decades, Hanoi has been strongly shaken by earthquakes such as 1961, earthquakes in Bac Giang with a strong magnitude of 5.6, in 1958 in Vinh Phuc province with a strong magnitude of 5.3. In 1953-1954, a magnitude 5.4 earthquake in Luc Yen district, Yen Bai province, but caused shock in Hanoi to level 8.

What recommendations do you have for forecasting and preventing earthquakes in our country?

Before each major earthquake, there was a long ' pre-stride ' period, probably tens of years. This is the process of energy accumulation, with small tremors occurring. A short time before the earthquake actually had a relatively large impact, then remained silent. Therefore, in order to predict, we need to have a seismic station system built all over the country. We now have 10 stations but in my opinion I need to increase more, especially in the Red River Delta because this is a densely populated area with many high-rise buildings.

The construction of buildings and high-rise buildings in Hanoi must have a design of seismic resistance at least level 7 (according to MSK-64 scale). In addition, depending on the ground, it is possible to reach level 9 such as weak land along rivers and alluvial grounds. In particular, for houses with dozens of floors, there must be a separate survey on the geological background at the construction site.

According to the earthquake partition map of 1 / 25,000 scale to serve the calculation of seismic resistance design for construction works, Hanoi ground is divided into 27 basic types of ground. The oscillation characteristics of each type of ground are determined according to earthquake repetition cycles of 200 years, 500 years and 1,000 years. Hanoi has also developed regulations on the application of standards