In 2011, just before an earthquake struck the east coast of Japan, nearby researchers recorded surprisingly high concentrations of the radioactive isotope pair: radon and thoron.

2011年，就在地震袭击日本东海岸之际，附近的研究人员侦测到了高浓度的放射性同位素组：氡和钍，对此他们十分震惊。