City decides to pursue first quakeproofing of Atomic Bomb Dome

by Aya Kano, Staff Writer

It was learned on January 23 that the City of Hiroshima will carry out the first seismic retrofitting of the Atomic Bomb Dome with a view to preserving this World Heritage site for years to come. Examination of the strength of samples taken from the dome’s walls have shown that some parts of the structure would be vulnerable in the event of a powerful tremor. After retrofitting, the dome will be able to withstand an earthquake measuring a lower 6 on the Japanese 7-point seismic scale, which has been predicted as a possibility if a massive earthquake were to occur at the Nankai Trough. Final preparations are now being made to include related costs in the initial budget for fiscal 2014.

As part of the inspection of the dome to assess its earthquake resistance, a project that began in fiscal 2007, the city government introduced the use of computer analysis for the first time in January 2012. Simulations have been conducted with earthquakes measuring a lower 5, as in the Geiyo Earthquake which shook Hiroshima in March 2001, an upper 5, and a lower 6, which is the estimated maximum intensity of a large earthquake occurring in the Nankai Trough. These simulations have shown that four sections of the dome, including those not supported by beams, would be subject to heavy stress.

To confirm the results of this analysis, the city commissioned a professional agency to collect cylindrical samples from 15 areas of the walls and analyze the strength of the bricks, among other items. It was decided that the dome is not in immediate danger of structural damage in the event of an earthquake with an intensity of lower 6, but strengthening work is necessary for the dome to survive such a quake intact.

The municipal government will pursue the design for executing the seismic strengthening work in fiscal 2014. Because the dome has been designated a historic site by the national government, the city will discuss the method used for the work with the Agency for Cultural Affairs. The dome went through major-scale preservation projects in 1967 and 1989, including the injection of bonding resin. But this will be the first seismic retrofitting for the structure.

The A-bomb Dome was added to the list of UNESCO World Heritage sites in 1996. In March 2006, the city government established a policy on the preservation and maintenance of peace memorial facilities. According to these guidelines, the city will not pursue major repairs on the dome, maintaining its present state until at least 2045, the 100th anniversary of the atomic bombing.

(Originally published on January 24, 2014)