A minor earthquake measuring 2.8 on the Richter scale hit Thanh Hoa on Wednesday.
It is the second tremor to be recorded over the past four days in the northern province.
Le Huy Minh, director of the Center of Earthquake Information and Tsunami Warnings, said the latest earthquake occured at just after 1 p.m. in Quan Son District. It lasted a couple of seconds and caused no casualties or physical damage.
This tremor was the aftershock from an earlier earthquake measuring 3.7 on the Richter scale that happened in the same place Sunday, according to Minh.
Nguyen Hong Phuong, vice director of the center under the Institute of Geophysics, said both the earthquakes happened around the Ma River, a known fracture zone.
The biggest-ever earthquakei n the southeast of Quan Son District was recorded in the 17th century with a magnitude of 6.7-6.8 on the Richter scale.