A research team has found a difference of 32.9 meters on average over the horizontal distances between ground zero in Hiroshima and the locations of some atomic-bomb victims at the time of the blast on Aug. 6, 1945, compared with previous measurements.
The finding may provide a better measurement of survivors' exposure to radiation and promote research on hibakusha-linked diseases, the research team leader, Norihiko Hayakawa, said in a recent interview with Kyodo News.
Hayakawa, an epidemiology professor at Hiroshima University's Research Institute for Radiation Biology and Medicine, said the recent study used as a sample 319 Hiroshima A-bomb survivors who were within about a 1-km radius from the hypocenter.
For the study, Hayakawa and his colleagues created a map that precisely indicated every house and building in the city of Hiroshima around the time of the blast.
The map was based on some 130 aerial photographs of the city on July 25, 1945, that the team obtained last year from the U.S. National Archives, according to Hayakawa.
Using the map as a base, the team remeasured the horizontal distance between the blast's center and victims within about a 1-km radius, and saw a 32.9-meter difference on average compared with past measurements, he said.
As a result, the distance between some A-bomb victims to ground zero became closer, while that of others became farther, Hayakawa said. Past measurements had been based on maps that were not as precise and dated around 1930.
Following up on the findings, Hayakawa said he and his team will further extend their study to cover A-bomb survivors within a 3-km radius, re-examine about 130,000 people, and probably make the necessary corrections.
Also, to examine their recent study's impact on shelters, the team is also mulling creating a three-dimensional map, he said.