 Although the claim was largely dismissed at the time, a 2012 analysis of radioisotopes suggested that North Korea may have performed two nuclear tests involving fusion.The paper was met with skepticism, as subsequent analysis of seismic data suggested no tests took place.In 2014, a study using seismic data found evidence for nuclear testing but a 2016 study once again dismissed claims of nuclear testing, suggesting that the seismic data was indicative of a minor earthquake.