학내 언론사

Kicker: DEBATE 

How Long Will South Korea Be in the Earthquake-safe Zone?

By Da-Hwee Kim, Editor-in-chief

elfnme@naver.com

  On January 9, 2023, at around 1:28 a.m., an earthquake of magnitude* 3.7 occurred in the 25 km sea area toward Ganghwa-gun, Incheon. It is the first earthquake of 3.5 or higher in 70 days since the Goesan earthquake in October and was recorded as the first earthquake of the new year. Minor earthquakes have occurred in Korea in the past, but as the fairly large earthquakes that occurred in Gyeongju and Pohang in the mid-2010s, doubts about whether Korea is truly an earthquake-safe zone have only grown.

  * magnitude: the great size or extent of something

Domestic earthquakes

  South Korea is known to be actually located inside the Eurasian plate. For this reason, seismic activity occurring on the Korean Peninsula cannot be explained by plate tectonics*. In addition, it is not directly in the seismic** zone. However, deep earthquakes hundreds of kilometers deep in the East Sea are believed to occur in the Benioff Zone of the Pacific Plate, which subducts obliquely under the Eurasian Plate from the Japan Trench. All other earthquakes occurring in and around the Korean Peninsula are also earthquakes that occur inside plates.

  * tectonic: relating to the structure of the earth's crust

  ** seismic: relating to earthquakes or other vibrations of the earth and its crust.

https://www.bgs.ac.uk/discovering-geology/earth-hazards/earthquakes/what-causes-earthquakes/

  In the case of Japan, Taiwan, and China, our neighboring countries, earthquakes occur frequently because they are located on the tectonic plate boundaries, and the damage they suffer from earthquakes is also quite large. Compared to this, it is easy to think that Korea is a safe place; yet it is absolutely forbidden to think that way.

Earthquake history in South Korea

  Official records related to earthquakes can be found in historical sources such as 'History of the Three Kingdoms', 'History of the Goryeo', and 'Annals of the Joseon Dynasty'. Nevertheless, those records are insufficient to conduct current seismic research. Still, it can be seen from these records that about 1,800 felt earthquakes occurred from AD 2.

http://english.hani.co.kr/arti/english_edition/e_national/819394.html

  Since the 19th century, relatively weak seismic activity has continued, and recently, in September 2016, the Gyeongju earthquake measured 5.8 on the Richter scale and in November 2017, the Pohang earthquake measured 5.4 on the Richter scale. What’s more, the number of minor earthquakes has increased considerably. According to the Korea Meteorological Administration's record of earthquake occurrence trends, the average number of earthquakes recorded in analog observations from 1978 to 1998 was 19.1. However, in digital observations from 1999 to 2020, an average of 70.6 earthquakes, more than three times higher, were recorded.

Small and frequent earthquakes, why should we not ignore them?

  Earthquakes are generally characterized by the fact that as the number of small earthquakes increases, the likelihood of a large earthquake increases. The status that many small earthquakes occur means that the accumulated forces in the fault* zone have been collected enough to cause earthquakes. A series of small earthquakes simply means that the fault is weakening. The weakened fault is greatly broken at once by the accumulated force in the crust, and a large earthquake may be induced. Therefore, an increment in the number of small earthquakes is never desirable in terms of seismic hazards.

  * fault: a fracture or zone of fractures between two blocks of rock

  Recently, studies on the relationship between seismic activity and earthquake structure in the Korean Peninsula have been conducted. But unfortunately, most of the data is high-altitude seismic data, so it is difficult to accurately estimate factors such as the epicenter or magnitude.

Discovery of active faults

  According to a recent government report on active faults, 16 places in the southeast area were analyzed as active faults. Furthermore, it is said that there are several active faults in the Chungcheong area. In this report, they analyzed quaternary faults of the Cenozoic Era or active faults with a high risk of earthquake recurrence. The analysis yielded very surprising results. The activity of faults was analyzed for the first time in Korea, and 14 active faults by section, including the Yugye segment of the Yangsan fault, were confirmed only in the southeast region of the Korean Peninsula. Including this result and the active faults investigated by the Ministry of Science and Technology, there are a total of 16 faults. We cannot help but feel a sense of fear with these findings.

  * quaternary: denoting the most recent period in the Cenozoic era

What actions to take during an earthquake

  It is virtually impossible to prevent natural earthquakes with human power. That is why it would be of great help if we knew, even at a personal level, what to do in case of an earthquake. Here are a few actions to take during an earthquake. First of all, if you are in a building, get under a table or desk and wait for the shaking to stop. If you are outside, be aware of falling objects and evacuate to an empty lot. And don't ride the elevator. This is because if you board an elevator during an earthquake, you may be trapped in it and unable to get out. There are many other evacuation tips, so please refer to the image below. 

Ministry of the Interior and Safety 
(xn--le5b23c9wbqa.com)

  South Korea may have been a safe zone from earthquakes before. Even so, who can be sure of the safety of the coming future? As mentioned above, seismic activity on the Korean Peninsula occurs inside the plate, so it is frustrating that there is no theory about it. I believe that our country also needs an attitude of constantly conducting scientific research and preparing meticulously in preparation for possible disasters without continuing to be too complacent.