Initial official surveys have concluded that a hydropower reservoir's operation has caused continuous tremors that have terrified locals in the northern province of Quang Nam since the end of last year.
However, at a meeting with local authorities on Thursday, Tran Tuan Anh, who led the survey team from the Vietnam Academy of Science Technology, stressed that operations at the Song Tranh 2 Hydropower Plant's water reservoir has only strengthened the fault zone activities at Bac Tra My District.
The fault zones were already active before the plant went into operation last December, according to Anh.
He said known as induced seismicity, such tremors will gradually stop when operations at the plant's water reservoir become stable.
The phenomenon, which refers to minor earthquakes caused by human activities that change the earth's crust, is "normal" and usually occur at places surrounding hydropower plants, he added.
Dr. Phan Trong Thinh, a member of the survey team, said although the team has yet to confirm whether the tremors will become stronger, usually induced quakes weaken as time goes by.
Meanwhile, Le Truong Son, another member of the survey team, said while the recent tremors' magnitude of 3.5 to 4 on the Richter scale isn't dangerous to the Song Tranh 2 plant, it can cause dangers to locals. A plan to evacuate people in risky areas is needed, he said.
On the other hand, leaders of Bac Tra My District, which has recorded increasing tremors since January and underground explosions on November 16-17, are still concerned.
Dang Phong, chairman of the district's People's Committee, said he is still worried because "initial conclusions aren't convincing and for sure."
Since the plant began operating, "abnormal" landslides have occurred at the district, especially at locations close to the plant, he said.
The academy should establish gauging stations at the district to study unusual landslides, said Tran Minh Ca, vice chairman of Quang Nam Province's People's Committee. It also needs to present official reports so that local authorities can explain it to locals, Ca added.
The academy launched the survey Wednesday, two days after Quang Nam's authorities sent a letter to it and the Ministry of Science and Technology asking for help in identifying shakings and underground explosions that are getting stronger in Bac Tra My District.