Mustaqim Adamrah, Jakarta – Jakarta's property management and control agency says land subsidence is occurring in the city, but there is no threat to buildings.

Agency head Hari Sasongko said Wednesday the subsidence was a natural phenomenon and would not endanger the capital's multi-story buildings, including the Sarinah building in Central Jakarta, which was built in the 1960s.

"Land subsidence occurs naturally in Jakarta where the soil is relatively young," he said at City Hall. "And high-rise buildings in Jakarta, including the Sarinah building, have been designed to handle this subsidence."

Tempo daily recently reported the Sarinah building on Jl. M.H. Thamrin was tilting. Hari acknowledged the land around the Sarinah complex was sinking, but said it did not pose a threat to the building.

"The main building, which has a strong foundation deep under the ground, is safe," he said. "The tilting building in the compound is an annex, which was built for automatic teller machines and is separated from the Sarinah building's main structures."

The annex, he said, was built on a shallow foundation that was unable to withstand the impact of the sinking land as well as a deeper foundation. Hari estimated the ground beneath the annex had sunk by up to six centimeters.

He said across the capital, there had been subsidence of between 20 cm and 40 cm over the past eight years. The city mining agency has said subsidence has accelerated in business districts where numerous high-rises have been built.

In addition to compressing the land, the buildings are also though to be depleting aquifers. The groundwater level in the Mega Kuningan business district in South Jakarta is dropping by five meters per year.

The mining agency said 80 percent of the city's land subsidence was caused by building construction, 17 percent by groundwater exploitation and 3 percent by natural causes.

To anticipate the possible future impacts of the subsidence, Hari said his agency would cooperate with the mining agency. This future cooperation might also involve a Bandung-based geology research center and the Bandung Institute of Technology, he said.

He hopes the parties can map land conditions across Jakarta. "We'll start with land conditions around buildings from Monas (Central Jakarta) to Semanggi bridge (South Jakarta)." He said the mapping would help land movement and serve as a reference for future construction.