The report quoted conclusions made by the Vietnam Academy of Science Technology as saying that the tremors in Bac Tra My District occurred during the operation of the Song Tranh 2 hydropower reservoir.

Previously the academy’s survey team had referred to the phenomenon as “induced seismicity,” which refers to minor earthquakes caused by human activities that change the Earth’s crust.

Tran Tuan Anh, head of the academy’s Geology Institute, said in the newspaper that the tremors will probably continue in the future with increased magnitude.

“But they will decrease as time goes by, and they will not exceed a maximum scale of 5.5 on the Richter scale that was estimated by surveys prior to the construction of Song Tranh 2,” he stressed.

According to Tuan, earthquake observation systems must be established soon around the hydropower plant’s site and across Bac Tra My District.

The academy started their surveys within the district on November 29 after local authorities sent a letter asking it to help identify the tremors and underground explosions that have been happening since last December when the plant became operational.

Bac Tra My’s People’s Committee said that about 200 tremors and underground explosions have hit the district, damaging many houses.

On December 1, the academy announced its initial conclusions that the tremors will stop gradually when dam operations stabilize. However, to quell public concern, the government ordered further inspections.

The Song Tranh 2 hydropower plant was built with an investment of more than VND4.15 trillion (US$197.53 million). Its output was expected to be 190 megawatts.

Thanh Nien News - December 31, 2011