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Yusuke Kawada, School of GeoSciences, University of Edinburgh (United Kingdom)
Hiroyuki Nagahama, Department of Geoenvironmental Sciences, Graduate School of Science, Tohoku University (Japan)
Yumi Yasuoka, Institute of Radioisotope Research, Kobe Pharmaceutical University (Japan)
Yasutaka Omori, Department of Geoenvironmental Sciences, Graduate School of Science, Tohoku University (Japan)
Tetsuo Ishikawa, National Institute of Radiological Sciences (Japan)
Shinji Tokonami, National Institute of Radiological Sciences (Japan)
Masaki Shinogi, Institute of Radioisotope Research, Kobe Pharmaceutical University (Japan)
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Precursory phenomena prior to the 1995 Kobe earthquake are investigated and compared. The fluctuation of crustal strain in the order of 10-6-10-8 is linked to preseismic changes in atmospheric radon concentration and groundwater discharge rate. In particular, the change in atmospheric radon concentration is expressed by the power-law and log-periodic oscillation model, and reflects the preseismic activation around the fault zone. The power-law change is due to the damage evolution process in the fault zone (internal system), while the log-periodic oscillation is affected by not only heterogeneities of stress field or geological structure in the neighbourhood of the fault zone but also external effects such as distant earthquakes. The external effect is considered as a trigger of the earthquake.
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