A small earthquake with underground explosion sounds in central Vietnam on Wednesday night might have been caused by a local hydropower dam, an expert says.
The earthquake was recorded in Quang Nam Province at a magnitude of lower than 3.5 on the Richter scale.
Dr Cao Dinh Trieu from the Institute of Geophysics at the Vietnam Academy of Science and Technology said the earthquake looked like the kind that occurs in areas with large reservoirs, news website VnExpress reported Friday.
Trieu said the Quang Nam earthquake might have occurred as water at the Song Tranh 2 reservoir had been absorbed to the zone of faults in the area and caused the seismic waves and the explosion sounds.
"People heard the sounds because the earthquake occurred very near the earth surface," he said.
Fearful locals fled from their homes in the middle of Wednesday night as the sounds were heard over a period of six hours through early Thursday.
Trieu said if more and bigger earthquakes are recorded in the area, the phenomenon will be studied further.
Local officer Tran Anh Tuan said ever since water was stored in the reservoir early this year, people in the area have been hearing explosion sounds from under the ground, mostly at night.
Tuan said the sounds were followed by small quakes on two other occasions this year in January and June.
The Song Tranh 2 hydropower plant was built with an investment of more than VND4.15 trillion (US$197.53 million). It started operation in December last year with an expected output of 190 megawatts.
The plant made headlines earlier this month, along with other hydropower plants in the region, for worsening the danger and impacts of floods by releasing water from their reservoirs. The floods killed 24 people.