Head of the Department of Seismology of the Institute of Astronomy and Geophysics of the Mongolian Academy of Sciences M.Ulziibat delved into the reason for the recent increase in the frequency of earthquakes in the following interview.

On average, how many earthquakes occur in Mongolia per year?

Last year, 39,950 earthquakes were recorded in the territory of Mongolia. Of these, 100 earthquakes were strong enough to be felt by humans. Earthquakes occurred 915 times in the area around Ulaanbaatar City. Among them, there are four earthquakes with a magnitude of more than three. On average, 200,000 to 400,000 earthquakes are recorded in one year, and about 200 times a month. The last strong earthquake was recorded in Ikhtamir soum of Arkhangai Province, reaching 4.7 magnitude.

Earthquakes are divided into categories: weak, medium and strong. Less than 3.5 magnitude is called weak. If it is more than that, it is stronger. It will also reach cities and towns 30 to 40 kilometers away. Magnitude above 5.5 is considered strong enough to cause damage. The last catastrophic earthquake happened in 2021 in Khankh soum of Khuvsgul Province, with a magnitude of 6.8. A team of international researchers estimated that the earthquake had a magnitude of seven. An earthquake with a magnitude of seven will cause a disaster if it is close to a city or town. Fortunately, no damage was incurred due to low population density in Khankh soum. Before that, in 2006 and 2010, the earthquakes with magnitudes of five to six occurred in the country.

Our country belongs to the seismically active region of Central Asia. The period with the most earthquakes in Mongolia was between 1900 and 1975. In 1905, the strongest possible earthquakes on the mainland were recorded four times. It crossed the lands of Uvs, Zavkhan and Khuvsgul provinces. In 1931, an eight-magnitude earthquake occurred in the southern part of the Mongol Altai. As a result, a rift about 370 kilometers long was formed. The last time, in 1957, there was a strong earthquake in Govi-Altai Province, and a 250 kilometers long crack was created. Between 1900 and 1975, Mongolia was the most seismically active region in the world. Compared to that time, activity has decreased now. But the danger is that new outbreaks are emerging. According to British scientists, the inactive earthquakes of 5,000 years ago may be reviving now.

The last strong earthquake was recorded in Ikhtamir soum of Arkhangai Province. In particular, two strong earthquakes happened in one day. What was the reason for this?

Four to five earthquake hypocenters are active. One of them is in Ikhtamir soum. Since the beginning of the year, there have been 300 earthquakes at the epicenter of the Ikhtamir earthquake. Of these, seven to eight were of a magnitude higher than 3.5 magnitude. The UK scientists called the earthquake occurring in Ikhtamir the Eg Pass’s fault. It is an 80 kilometers long crack. The epicenter is close to the Eg Pass.

Second, traces of extinct volcanoes have been found in regions where the earthquakes are occurring. It is believed that it depends on it. Starting from this week, we are working to determine the cause in detail through our stations.

Where are the epicenters of the four active earthquakes?

The earthquake zone in Khankh soum of Khuvsgul Province is still active. The tremors are repeated after a strong earthquake. More than 100,000 aftershocks were recorded in Khankh soum within a year after the earthquake. Six magnitudes have been recorded three to four times. An earthquake means that the ground has cracked and broken deep within the earth. A broken place keeps trembling.

The next one is the Ulaanbaatar area, which has attracted attention since 2005. The frequency of earthquakes around the capital has grown. As a result of our research, we determined that this is a process that is taking place according to natural activation. Around Ulaanbaatar, there are six cracks. Because of them, earthquake activity increases. Another problem is that earthquakes of an unprecedented magnitude have been recorded several times in the city. When the earthquake occurred in Gachuurt (east side of the city), the whole of Ulaanbaatar felt the tremors. The earthquake was also felt in Emeelt (west side of the city). There is a 80 kilometers long fault in the Khustai Mountain range. The ground shook twice there. Ikhtamir soum has become an active earthquake zone since 2022. About 5,000 to 6,000 earthquakes have happened there since 2022.

You mentioned six cracks near Ulaanbaatar. However, recently there has been talk about the emergence of the seventh rift, right?

For three years since 2012, we had conducted a study of earthquake activity in the vicinity of Ulaanbaatar in collaboration with French, Portuguese and Russian scientists. As a result, we identified six possible foci of strong earthquakes. However, in 2020, scientists from Japan and the National University of Mongolia conducted joint research and found the seventh rift. It is a 50-kilometer fault that runs from the back of Bogd Khaan Mountain through Ulaanbaatar to the slopes of Naran.

Why were six to seven faults so close to each other in terms of region?

Ulaanbaatar city is located in an active earthquake zone. It has been determined that these cracks were formed by a strong earthquake about 1,000 years ago.

According to the regional map of earthquake activity, the southern and central parts of Mongolia are more at risk. Can you elaborate on this?

There are relatively few strong earthquakes around Ulaanbaatar. However, the reactivation of previously active foci is dangerous. Earthquakes similar to those recorded in Khankh soum in Khuvsgul Province and Deren soum in Dundgovi Province will cause a disaster in Ulaanbaatar. Earthquake scientists pay attention to our country due to the fact that it suffered very little damage from strong earthquakes. There is an example of a city being destroyed by a 4.6 magnitude earthquake. Then, tremors of this magnitude occur frequently in Mongolia.

Last year, Turkey and Syria suffered major earthquakes. Is there a risk of such a danger in Ulaanbaatar?

Yes. Even if an earthquake occurs less strongly than in Turkey, there will be danger. The buildings’ quality shows it. Cracks occur within a few months of moving into a new apartment in Mongolia. It is obvious what will happen during strong earthquakes when a building is collapsing itself.

What actions are being taken to prevent earthquakes?

The Govi-Altai fault is likely to cause an earthquake with a magnitude of 8.1. Therefore, a warning system has been installed in Ulaanbaatar before a strong earthquake. It is a station to study the pre-earthquake process. In this way, its magnitude is determined by the nearest station to earthquakes. It will determine the force in the first 10 seconds. There is a distance of 190 kilometers from the Deren soum point in Govi-Altai Province to Ulaanbaatar. If we assume that the tremors of the earthquake will spread three kilometers in one second, it will take about 65 seconds to reach the capital. So, it is possible to warn citizens only 55 seconds before. In other words, people ask, “What will we do in 55 seconds?” The Japanese officials say, “If you practice well, this is a long time.” They confirmed it. In Japan, students are informed and disaster prepared. As a result, it takes only 15 seconds for 20 to 30 children in one class to go to a safe place.

Does the epicenter in Khankh soum of Khuvsgul Province affect the occurrence of earthquakes in other areas?

It is relatively less likely to affect others. Recently, however, earthquakes caused by human activity have been observed. As can be seen from the map of the frequency of earthquakes, the eastern provinces have hardly faced such danger before. However, due to oil extraction, strong earthquakes have been recorded. For this reason, four to five earthquakes have been reported recently. It means that the region doesn't have an active epicenter, but earthquakes occur strongly there.

There are many mining companies in the eastern provinces, right?

It is essential to consider what mining activities will affect it. When fluids are pumped deep into the ground, they cause vibrations. These are called human-induced earthquakes. For example, “Petrochina Dachin Tamsag” Company pumped a lot of water underground during oil extraction for many years. It affects the occurrence of earthquakes. This conclusion was reached because the earthquakes happened in the oil extraction area of the company.