HANOI - More than 20 earthquakes have struck Vietnam's central Quang Nam province, 650 km south of capital Hanoi, since the start of this month, causing concerns to experts and worries to local people, local media reported on Monday.

As many as seven earthquakes occurred within 13 hours, from 10 pm last Saturday to 10:57 am last Sunday in the provinces Bac Tra My district, with the last one, a 4.8-magnitude, 10-second quake, as the strongest to hit the area so far.

Local people showed great concern as the Song Tranh 2 Hydropower Plant, the biggest of its kind in the central region with a reservoir storage of more than 730 million cubic meters is in the area.

According to experts from Industrial Safety Techniques and Environment Agency under the Ministry of Industry and Trade, the Song Tranh dam is designed to resist a 5.5-magnitude or higher quake. Theoretically, the sequence of tremors caused by water storage will continue recurring but is expected to be no more than 5.5 on the Richter scale.

Meanwhile, Le Huy Minh, deputy director of the Geophysics Institute, under the Vietnam Academy of Science and Technology, said that the Song Tranh plant was built on an area with active faults. These active faults caused earthquakes and tremors even when the plant's reservoir had not been built.

According to the Institute's statistics, from 1715 to 1992 before the plant was built, only eight minor quakes were recorded in the areas.

Local people called for a pause to water storage during the flood season, and the installation of equipment to closely monitor earthquakes.