The earthquake that occurred in Nho Quan District, Ninh Binh, on the morning of May 27, was attributed to the activity along the Da River fault line, classified as a second-order fault, according to experts from the Institute of Geophysics.
According to the Earthquake Information and Tsunami Warning Center (Institute of Geophysics), an earthquake measuring 3.4 on the Richter scale struck Nho Quan at 9:27 AM, at a depth of 17 kilometers. It was accompanied by a small explosion sound, and the ground shook lightly. Residents in Thach Thanh and Ha Trung Districts in Thanh Hoa Province, near the epicenter in Nho Quan, also felt the tremors.
In an interview, Associate Professor Dr. Nguyen Hong Phuong, a seismic expert at the Institute of Geophysics, stated that the tectonic earthquake originated from the Da River fault line, which is quite well-known for its activity level. The area affected is in Ninh Binh, close to major cities like Hanoi, which is why residents experienced noticeable tremors and sounds. “This is a minor earthquake and does not fall under the category of dangerous earthquakes,” he said.
Epicenter location. (Photo: Institute of Geophysics).
The Da River fault is a source of moderate earthquakes in northern Vietnam. Dr. Hong Phuong mentioned that the fault zone is divided into two categories (first-order and second-order). First-order faults can cause significant earthquakes, such as those in Dien Bien, Tuan Giao, and Son La, while the second-order Da River fault typically leads to minor tremors.
Second-order faults separate two tectonic regions, between Son La and the Da River, as delineated by geologists on the map. This fault zone is located in the Northwest of northern Vietnam, stretching 450 kilometers in a Northwest-Southeast direction, running from the Pa Nam Cum area (Lai Chau) through Quynh Nhai and out to the East Sea at the mouth of Lach Giang.
A similar earthquake was recorded in Ninh Binh in 2005. Experts indicated that while this minor earthquake has a natural disaster risk level of zero, it is essential to monitor developments regularly, as earthquakes often occur in sequences. The Institute of Geophysics is currently monitoring any aftershocks and will issue notifications if there is a higher danger level.
Dr. Nguyen Xuan Anh, Director of the Institute of Geophysics, also noted that Ninh Binh, located on the Da River fault line, is an area that has experienced earthquakes before, so the earthquake that occurred this morning is not unusual.
Tectonic earthquakes are caused by natural fault lines (a geological phenomenon related to tectonic processes within the Earth’s crust). Typically, faults occur in areas with unstable geological conditions. The earthquake in Ninh Binh originated from the Da River fault, which differs from the induced earthquakes previously recorded in Kon Plong District, Kon Tum Province. Induced earthquakes are caused by human activities affecting the environment, specifically occurring in hydropower areas where reservoir pressure leads to triggered seismic events.
