”Are sinkholes man-made disasters?” A report from two years ago also puts land subsidence risk at level 4 = South Korea

It has been confirmed that the area where a large sinkhole occurred, which led to the death of a motorbike driver in his 30s in South Korea, was also identified as a region requiring attention in a Seoul city utility report two years ago.
According to the report on the "Seoul Metro Line 9 4-stage Extension Project Underground Safety Impact Assessment Service" submitted by Seoul City to the office of Democratic Party lawmaker Park Young-gap on the 28th,
The analysis revealed that the ground around the point is weak and the amount of subsidence is large. The report, which was commissioned by Seoul City in 2021 and completed in 2023, outlines the risk of subsidence due to the extension work of subway line 9.
The purpose of the report was to investigate the cause of the accident. The 939 bus stop fault zone section (near the accident site) had a relatively large amount of subsidence, and excavation work was carried out in this section, as well as the installation and dismantling of temporary facilities.
"When carrying out the tunnel construction, it is necessary to pay attention to the measurement results and carry out the construction safely," he explained. The area is a "fault fracture zone" where rocks have been deformed and continuity has been interrupted, so the construction of the tunnel is
In addition, waterworks pipes run through the area, and there are concerns that excavation could cause groundwater to flow in and weaken the ground, leading to a land subsidence risk rating of 4 or higher.
In addition to this report, there have been other warnings of land subsidence concerns in the area. In April 2021, the Korean government announced that there were concerns about land subsidence due to construction of the extension of Route 9.
The National Tunnel Environment Society's official documents were submitted to the city. Seoul city also categorized the area as Level 5, the highest risk of sinkholes.
Despite this, the on-site inspection was not carried out properly, and the accident was in fact man-made.
Following the sinkhole incident that occurred on Seongsan-ro, Yeonghui-dong, Seodaemun-gu last year, the city started conducting GPR surveys once a month in areas at risk of subsidence.
However, due to issues with contracts and other administrative procedures, the investigation was not carried out until this month.