Research by academics from two major universities has come into question after data from a notably strong earthquake in Mashiki, Kumamoto Prefecture, was found to contain errors, according to a person involved.
The science ministry is looking into whether quake-strength data collected by the team of researchers from Osaka University and Kyoto University was falsified or fabricated due to inconsistencies with other readings taken nearby.
The researchers removed the data in question from a website where it had been posted in July 2016.
The research centers on the magnitude 7.3 jolt on April 16, 2016, that followed another powerful temblor around 28 hours earlier. Both quakes registered a maximum 7 on the Japanese seismic intensity scale in hardest-hit Mashiki, making it the first case in which the same location had the highest reading twice, according to the Meteorological Agency.
There is no indication that the data in question affected government reports on the quake or related policies, according to a division studying quake and disaster mitigation under the science ministry.
The team had announced the quake was measured as having an intensity of 6.9 on the Japanese scale at an observation point south of the Mashiki town office, which was notably stronger than nearby spots. The figure was based on data measured by a seismometer temporarily installed April 15 following the first quake.
The group had also reported that the strong jolt triggered the collapse of many wooden houses in the area. Details of how the data was handled were not immediately available, as no members of the team responded to questions from Kyodo News.
But Hiroyuki Goto, a Kyoto University associate professor and one of the team members, admitted in a post on his website that the study contained “problematic” data and that “there is no doubt” that he helped disperse it. “I deeply apologize,” he said in the statement.
Goto said he discovered that the seismic wave shown in the data was unnatural after receiving an anonymous tip in late September, which was also sent to the Japan Society of Civil Engineers.
Goto also admitted that he had received a similar question from another anonymous person last December but did not review the data at the time.
The data had shown that “unpredictably” strong shaking occurred in Mashiki and research to get to the bottom of the mechanism had subsequently taken place, according to Goto. “After all, we have ended up disappointing people who have been involved in the study,” he said.
The team has issued research papers based on the data, but Goto said on his home page that he will take steps to retract them.
The Meteorological Agency has said the Kumamoto quake registered an intensity of 7 in Mashiki based on data taken from measurement devices different from those used by the team.