Seoul City has discovered 105 underground cavities after four months of high-tech ground inspection. According to the city government Wednesday, during its inspection of 48-kilometer section of arterial roads previously connected to cave-in accidents, 105 potential sinkholes were detected.

With an additional 246-kilometer section to be scanned this year, an estimated 195 more cavities are expected be found. The latest investigation began in the wake of February 2015’s sinkhole accident in front of Yongsan train station in Seoul. Last year, 56 sinkholes were detected in the city.

In the safety inspection that ensued, Ground Penetration Radar-mounted vehicles scanned the surface, then a portable GPR identified the exact location of the cavity and then the ground was drilled open to check the size of the hollow space beneath. FULL REPORT