'The culprit' causes earthquakes to be hydropower reservoirs?

After the earthquake in Lai Chau in the last days of April 2011, on May 7, a magnitude 4 earthquake occurred in Son La. Many people question the "culprit" as reservoirs. Someone said, this is just a common aftershock of the previous earthquake.

Due to hydroelectric reservoir?

Professor Nguyen Dinh Xuyen, former director of the Institute of Geophysics, said that it is true that in 2011, in most major earthquake belts in the world, earthquakes seem to take place more than years. The reason is that Japan's 9-magnitude earthquake has impacted and stimulated the other earthquake belts.

For our country, there is no concrete evidence that Vietnam is affected by the Japanese earthquake. If so, it is probably only indirect effects that we cannot see. Since the beginning of the year, our country has recorded some earthquakes. For Son La and Lai Chau, areas in the past have also experienced earthquakes. The cause may be due to endogenous factors because these areas are located on the fault zone. However, it may also be due to the impact of hydropower reservoirs.

Earthquakes caused by external agents such as hydropower reservoirs and reservoirs . only occur within a radius of 30km around the dam lake.

Prof. Dr. Pham Hong Giang, Big Dam Association said that there has been no basis to confirm the existence of hydroelectric dams affecting the formation of earthquakes . The successive earthquakes in the Northwest region are because they are located in the fault zone from the underground, but there is no basis to confirm that it is the impact of dams. Large lakes in the world have never happened before.

Dr. Le Tu Son, Head of Earthquake Observation Department, Institute of Geophysics , said that the earthquake is also called earthquake due to external agents such as hydroelectric reservoirs, reservoirs . only happen out in a 30km radius around the dam lake. The recent earthquakes all happened far away from the reservoirs, so it can be confirmed that these are natural earthquakes.

Great earthquake in the rainy season

According to Engineer Nguyen Van Yêm, former official of the Tsunami and Tsunami Warning Center, the earthquakes in Lai Chau and Son La in recent years are not too unusual. The northwest is the area that is predicted to have many earthquakes. The frequency of earthquakes is also different each year, there are up to 10 earthquakes every year, but there are only a few appearances a year.

Dr. Le Tu Son also said that these are unusual earthquakes, the aftershocks of the previous strong earthquakes and it will last 1 to 2 months before stopping. If the following earthquakes are stronger than the previous one, then it may be considered unusual. These aftershocks are normal, hard to avoid and nothing to worry about.

However, there is also an unclear rule that, in the rainy season until the end of the rainy season, earthquakes occur more. The reason is that, water will soak into the ground, changing the sliding friction in the ground to stimulate earthquakes. Accordingly, there are earthquakes that should have happened in the next few years, but due to the change in sliding friction, the earthquake took place faster.

The earthquake in Binh Thanh and Hoa Binh in 1986 is a typical example. At that time, the newly-built 86m hydroelectric reservoir caused a magnitude 4.9 earthquake.

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