The Seoul Metropolitan Government announced Sunday that it will strengthen ground subsidence monitoring to prevent future sinkhole accidents across the city. Public concern has risen sharply since a deadly sinkhole incident occurred in Gangdong-gu on March 24.
A motorcyclist tragically died after falling into a 20-meter-wide and 18-meter-deep sinkhole. Since then, authorities have identified around 50 at-risk locations throughout Seoul, prompting urgent action. Officials decided that enhanced ground subsidence monitoring offers a stronger defense against similar disasters.
The new system involves installing a bat-shaped column sensor 20 meters underground at key sites. This sensor’s antenna can detect changes within a 50-meter radius and immediately send the data to a central monitoring station. Once any irregularities are found, officials can act swiftly to prevent accidents.
Previously, Seoul relied on the Ground Penetrating Radar (GPR) system, which sends high-frequency waves underground to detect cavities. However, the GPR system only works effectively up to two meters below ground, limiting its usefulness. Therefore, city officials saw the need for a deeper, more reliable ground subsidence monitoring approach.
By May, Seoul plans to install the first ground subsidence monitoring system at a construction site near the March sinkhole. At that location, construction had been underway to extend Seoul Subway Line No. 9, a project now suspended due to safety concerns. Officials acknowledged that nearby construction could have contributed to the accident.
Most large sinkholes start forming about 10 meters underground, making the new system more suitable for early detection. City officials believe that ground subsidence monitoring will overcome the limitations of previous methods, helping to safeguard Seoul’s infrastructure.
However, challenges remain with the new system. Unlike mobile GPR units that scan large areas from vehicles, fixed sensors only monitor specific spots. Therefore, the city plans to deploy ground subsidence monitoring at major construction sites while continuing GPR surveys for broader coverage.
Meanwhile, a large-scale safety inspection took place in Gwangju on April 23. The government ordered nationwide inspections at all major construction sites until late May to prevent further sinkhole incidents.
Separately, the central government allocated 2.27 billion won ($1.5 million) in its supplementary budget to support ground exploration efforts. Some uncertainty remains about the effectiveness of this investment. Although additional equipment purchases are planned, limited exploration depths could hinder detection efforts.
Authorities had considered introducing deeper-penetrating GPR systems earlier this year. However, they canceled the plan due to doubts about the unproven technology’s performance. Despite these hurdles, both the Seoul Metropolitan Government and the central government remain committed to strengthening ground subsidence monitoring across the country.
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