VietNamNet Bridge – Scientists of the Institute for Science and Technology of Vietnam have concluded that underground explosions in the downstream area of Song Tranh 2 hydro-power plants in Bac Tra My district, Quang Nam province were caused by Song Tranh 2 reservoir induced seismicity, not the operation of volcanoes.

The conclusion was made after one month of research based on data of the Geophysics Institute. Experts said that this is a normal phenomenon and local residents should not be so worried about it.

The Geophysics Institute has recorded around 100 earthquakes of this type in Vietnam. At the Hoa Binh reservoir, one of the biggest hydro-power works in Vietnam, scientists recognized earthquakes of 4.8 of the Richter scale before the reservoir stores water. Earthquakes repeated in 4-5 years later with reducing frequency and intensity.

This phenomenon is also common in the world. Exceptionally, it prolonged to 20-40 years for some hydro-power works, for example the Koyna reservoir in India.

Dr. Tran Tuan Anh, director of the Institute of Geology, said that earthquakes of less than 3.5 Richter scale will continue in Bac Tra My district but they will gradually reduce. Earthquakes there will be unable to exceed 5.5 Richter scale, he confirmed.

Scientists asked competent agencies to assist Quang Nam province to install observing stations in Bac Tra My district.

According to the authority of Bac Tra My district, since Song Tranh 2 hydro-power plant built its dam to store water in late 2010, around 200 earthquakes and underground explosions have been recorded, including four in November 2011 alone. In the latest case, which happened at 9.30pm, November 27, a big explosion with aftershock in a 30km diameter was recorded.

This phenomenon has caused abnormal landslides and depression in the region. Some houses have cracked walls and foundations. The local authorities are worrying that if the phenomenon continues, ethnic minority people will move deep into the forest, resulted in deforestation. If earthquake increases to five Richter scale, many houses will collapse.

Mai Chi