New earthquake cycle in Vietnam?

The aftershock of the 4.7 magnitude earthquake occurred at 9 pm on June 23 near Phu Quy island (Binh Thuan), causing Ho Chi Minh City to shake. The earthquake is not large, but according to some experts, this could be a sign of a new earthquake cycle .

According to Prof. Lam Minh Triet, Ho Chi Minh City Institute of Physics, the earthquake took place in Binh Thuan sea area in the Thuan Hai - Minh Hai fault system. This is one of the most active fault faults of 14 fault systems in the Southern region.

Historically, the fault system of Ninh Thuan's sea had an earthquake up to 5.5 richter. According to some observations in the professional world, this region may occur earthquakes greater than 6 richter.

Special attention is needed

Dr. Cao Dinh Trieu, Vice Chairman of Asian Seismic Association, Secretary General of Vietnam Geophysical Association, said that yesterday's earthquake was not in the Thuan Hai - Minh Hai fault system, but Nam Con fault. Sơn, for lying about 150 km from the shore.

There are two views in specialized scientific circles: Faulty systems in this area cannot have strong earthquakes. Protection for the above view, this group put forward, the observed earthquakes are not strong.

The suspected fracture occurred earthquake on June 23, line 14, located near the 3rd road (adjacent 2s).

In 1877, the earthquake in Binh Thuan occurred 3 times. By 1882, also in this region, earthquakes and high waves occurred (possibly tsunamis). Documents from the US Geological Survey recorded two above magnitude earthquakes and small tsunamis. Therefore, earthquakes caused by the Thuan Hai fault zone - Minh Hai may be as strong as 7.5 Richter. The Nam Con Son fault may be weaker, but may also cause an earthquake of between 6 and 6.5 on the richter scale.

According to Dr. Cao Dinh Trieu, large earthquakes have been cyclically recorded in history, in 1877, 1822, and 1923 and in recent years these small earthquakes have been constantly happening. Pay special attention, follow up. Maybe this is a sign of a new strong earthquake cycle.

According to Dr. Cao Dinh Trieu, Vietnam's biggest difficulty is that there are not enough warning stations but most of them are concentrated in the North. Even in Binh Thuan and Vung Tau areas with the Thuan Hai - Minh Hai and Nam Con Son faults, there are no stations yet. The nearest station is in Nha Trang, Da Lat .

In terms of capacity of Vietnam's stations, it is only 'temporary', can not solve itself but must rely on the world, such as the US Geological Survey (USGS), global earthquake monitoring system (GEOFON) .

The fact that these two agencies have not yet posted their 4.7-magnitude earthquake in Binh Thuan sea may be because the earthquake is small and not dangerous. Dangerous earthquakes and possible damage must be above 5 richter.

Disaster risk

Meanwhile, MA Do Van Linh, deputy head of the Southern Geological Mapping Division, said that the territory from Song Cau (Phu Yen) to Mui Ca Mau, Nam Con Son has about 22 faults possible. earthquake.

The earthquake fracture that occurred on June 23, probably not among the faults of the region's largest earthquake, is just a secondary fault. First-class fracture, possibly the largest earthquake in this area, is the Thuan Hai - Minh Hai fault and the fault in the meridian 109. However, the determination of the earthquake on June 23 involves Which fault should continue to monitor and study.

According to MS Linh, it is difficult to predict whether earthquakes followed the earthquake on June 23 or not. However, monitoring this area in recent years has shown that there are many small earthquakes, which can signal this is a strong earthquake. Mr. Linh's research and other scientists have suggested that the earthquake cycle of this area is about 50 years.

About faults that are likely to cause earthquakes directly affect HCMC as the Saigon River fault and Vam Co Dong river fault, recent observations, only see earthquakes from 1.5 to 2, 7 richter. Forecasting, secondary level faults in the South Central region can generate earthquakes not exceeding 7 richter, ThS Linh also said.

According to MS Linh, the fact that people in high-rise buildings in Ho Chi Minh City clearly felt when there was a seismic earthquake due to the weak ground and a large fluctuation range. MS Linh warns, the status of works is less attention to calculating seismic resistance when building, if an earthquake occurs from 5.5 Richter or more, the risk is difficult to say.

How to escape when an earthquake occurs

If an earthquake occurs while indoors, you need to crawl under a large table or bed. Without a table, you need to stand in the corner of the room or door. If the power goes out, you should use a flashlight, do not use candles or matches because it can cause a fire. If an earthquake occurs while on the street, you need to stay away from buildings and wires, find a place to stay in the empty space. If an earthquake occurs while driving, you need to stop at the curb, avoid electric poles, wires, and bridges.

If you experience a strong earthquake, you need to check if anyone is injured. Do not move injured people unless they are near wires or other dangers. If the house collapses, you need to make a sound to call for help.

In addition, you also need to prepare for aftershocks, earthquakes caused by an earthquake that just happened, although they are smaller, they can still cause injuries.