VietNamNet Bridge – Up to 11 out of the 27 quakes occurred in the district of Bac Tra My in the central province of Quang Nam, and experts say that more quakes are expected to occur in this area.

According to the Center for Earthquake and Tsunami Warning of the Institute of Geophysics, so far this year Vietnam has had 27 earthquakes with a magnitude of 2.5 to 4.7 on the moment magnitude scale.

Bac Tra My district had up to 11 quakes; followed by Son La province with 9; Dien Bien with 2; and the provinces of Thua Thien - Hue, Lao Cai, Nghe An, and Quang Ngai with one each.

Dr. Nguyen Xuan Anh, director of the Institute of Geophysics, says that compared with 2012, the magnitude and frequency of quakes since early 2013 have tended to decrease.

"But there is no sign that earthquakes will end, so we need to continue monitoring the phenomenon and focus our research on the relationships between quakes and the Song Tranh hydro-power reservoirs," he adds.

The Institute of Geophysics has deployed its geological monitoring network in the area of the Song Tranh 2 hydro-power plant in Bac Tra My district of Quang Nam province.

The expert says that in recent years, only medium and small earthquakes occurred in the territory and continental shelf of Vietnam, but in 1983 an earthquake off 6.8 on the Richter scale occurred in Tuan Giao, Lai Chau province.

According to scientists, the epicenter of the quakes were no randomly distribute, but focused on specific fault zones, specifically the Muong La - Bac Yen, Son La and Song Ma in the north and the continental shelf off the coast of Vung Tau in the south.

The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of the area that slipped.

The scale was developed in the 1970s to succeed the 1930s-era Richter magnitude scale. Even though the formulae are different, the new scale retains the familiar continuum of magnitude values defined by the older one. 

Na Son