Power-law and log-periodic changes in precursory phenomena prior to large earthquakes
|Location||International Geological Congress,oslo 2008|
|Author||Kawada, Yusuke۱; Nagahama, Hiroyuki۲; Yasuoka, Yumi۳; Omori, Yasutaka۲; Ishikawa, Tetsuo۴; Tokonami, Shinji۴; Shinogi, Masaki۳|
|Holding Date||08 September 2008|
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.