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“The repeat of earthquakes in this region recently are dangerous and the phenomenon must be researched seriously,” said Prof., Dr. Cao Dinh Trieu from the Geophysics Institute.
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.
On November 30 and December 1, scientists made a field trip in 24 communes in Bac Tra My and Nam Tra My districts to define the epicenter of recent earthquakes.
According to the Institute of Science and Technology of Vietnam’s initial conclusion, underground explosions in the region were caused by reservoir induced earthquakes of 3-4 Richter scale from the fault on the left bank of Tranh River.
The capacity of Song Tranh hydro-power plant’s reservoir is over 730 million of cubic meters, which is located over 100m higher than the downstream area. Experts worry that if the dam is broken, it will cause disaster to the downstream region. It is predicted that the reservoir can cause maximal earthquake of up to 5.5 Richter scale.
In December 1967, a 6.3 Richter scale earthquake, which was rated as reservoir induced earthquake, occurred in Koyna, Indian, killed around 200 and injured around 1,500 others.
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