Revisiting the Kobe Earthquake and the Variations of Atmospheric Radon Concentration

Using data from the 1995 Kobe Earthquake, researchers have uncovered a better understand about radon concentration in the atmosphere before and after earthquakes. The findings move us closer to being able to predict when large earthquakes will occur.

Co-author Yumi Yasuoka points to data from the radon measuring instrument

Tohoku University researchers have unearthed further details about radon concentration in the atmosphere before and after earthquakes, moving us closer to being able to anticipate when large earthquakes may hit.

The results of their research were published in the journal Science Reports on February 18, 2021.

Radon is a radioactive noble gas derived from radioactive decays of radium-226 in the ground. Radon bubbles up to the surface and is expelled into the atmosphere.

It has long been known that elevated levels of radon underneath the ground can be detected before and after earthquakes. But the relationship between the mechanisms that cause abnormal changes in radon concentration and the occurrence of earthquakes requires greater understanding in order to predict earthquakes accurately.

Professor Hiroyuki Nagahama and associate professor Jun Muto of the Graduate School of Science at Tohoku University, in collaboration with Fukushima Medical University and Kobe Pharmaceutical University, analyzed radon concentration data observed before the 1995 Kobe Earthquake.

Atmospheric radon concentration observed before the 1995 Kobe earthquake. Periodic analysis was performed on the data between 1984 and 1988 and the data between 1990 and 1994. Missing data is from 1989

"We found that there were changes in radon concentration data that originated from tides," said Muto. "This caused periodic loading on the earth's crust."

They also noticed that crustal compression rates on faults near the radon observation point had decreased, and this may have triggered the periodic change in radon concentration.

Radioisotope facilities, which measure the atmospheric radon, exist across Japan.

Muto hopes that their research leads to an increase in radon monitoring across the globe. "We believe that further examination of seismological and geological conditions that differ from Japan will lead to a better understanding of the physical and chemical processes that cause radon concentration variations preceding earthquakes."



Jun Muto
Graduate School of Science, Tohoku University
Email: [email protected]

Published: 04 Mar 2021


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Title: Radon degassing triggered by tidal loading before an earthquake
Authors: Yasutaka Omori, Hiroyuki Nagahama, Yumi Yasuoka & Jun Muto
Journal: Scientific Reports
DOI: 10.1038/s41598-021-83499-0

Funding information:

The present study was financially supported by JSPS Grants-in-Aid for JSPS Fellows (08J06445 to Y.O.) and Early-Career Scientists (18K13620 to Y.O.) and by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan under its Earthquake and Volcano Hazards Observation and Research Program (1207 and THK_10 to H.N.).