Earth Planets Space, Vol. 63 (No. 3), pp. 301-314, 2011
Takeo Ishibe1, Kunihiko Shimazaki1,2, Hiroshi Tsuruoka1, Yoshiko Yamanaka3, and Kenji Satake1
1Earthquake Research Institute, the University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-0032, Japan
2Association for Earthquake Disaster Prevention, 5-26-20 Shiba, Minato, Tokyo 108-0014, Japan
3Research Center for Seismology, Volcanology and Disaster Mitigation, Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
(Received June 25, 2010; Revised January 26, 2011; Accepted January 27, 2011; Online published March 4, 2011)
To determine whether current seismicity continues to be affected by large historical earthquakes, we investigated the correlation between current seismicity in Japan and the static stress changes in the Coulomb Failure Function (ΔCFF) due to eight large historical earthquakes (since 1923, magnitude ≥ 6.5) with a strike-slip mechanism. The ΔCFF was calculated for two types of receiver faults: the mainshock and the focal mechanisms of recent moderate earthquakes. We found that recent seismicity for the mainshock receiver faults is concentrated in the positive ΔCFF regions of four earthquakes (the 1927 Tango, 1943 Tottori, 1948 Fukui, and 2000 Tottori-Ken Seibu earthquakes), while no such correlations are recognizable for the other four earthquakes (the 1931 Nishi-Saitama, 1963 Wakasa Bay, 1969 Gifu-Ken Chubu, and 1984 Nagano-Ken Seibu earthquakes). The probability distribution of the ΔCFF calculated for the recent focal mechanisms clearly indicates that recent earthquakes concentrate in positive ΔCFF regions, suggesting that the current seismicity may be affected by a number of large historical earthquakes. The proposed correlation between the ΔCFF and recent seismicity may be affected by multiple factors controlling aftershock activity or decay time.
Key words: Background seismicity rate, static change in the Coulomb Failure Function (ΔCFF), recent seismicity, large historical earthquakes.