Roughly a third of bridges and highways here have not been retrofitted to withstand earthquakes, causing safety concerns in light of the devastating quake in Japan, said Seoul officials Tuesday.

According to the Seoul Metropolitan Government, 111 bridges, highways and overpasses are in need of retrofitting, out of a total 348 located throughout the capital.

City officials said, however, that all of the roughly 20 larger bridges that span the Han River have top notch seismic ratings, as they were either built as earthquake resistant or retrofitted sometime afterward.

“In the past, earthquake resistant designs were not mandatory. Therefore, buildings were not retrofitted, and we became aware of the problem rather recently,” said a city official.

“We have started seismically retrofitting the bridges since 2005, centered on the older ones,” he said.

The city plans to spend a total of 131 billion won ($115 million) seismically retrofitting transit facilities in the future and has already spent 6.5 billion won seismically retrofitting 16 bridges.

According to the official, the bulk of the projects will be completed by 2015.

By Robert Lee (rjmlee@heraldcorp.com)