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Method for prediction of off Ibaraki M7 characteristic earthquakes based on seismicity change. Shozo Matsumura (NIED). B: 2008M7.0. A: 1982 M7.0. Seamount discovered by Mochizuki et al. (2008). Recent Characteristic Earthquakes off Ibaraki Prefecture.
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Method for prediction of off Ibaraki M7 characteristic earthquakes based on seismicity change Shozo Matsumura (NIED)
B: 2008M7.0 A: 1982M7.0 Seamount discovered by Mochizuki et al. (2008) Recent Characteristic Earthquakes off Ibaraki Prefecture
One Century History of Characteristic Earthquakes Sequence off Ibaraki Prefecture 27.4y 19.9y 22.4y 16.8y 25.8y ? a 2027 - 2035 b A B C d1 c d2
Event A Event B Micro-seismicity observed by NIED for 30 years
2007.7.8. – 2007.12.7. 2007.12.8. – 2008.5.7. Micro-earthquake Density Maps before event B Ratio of Density Maps Before event B
Before event Correlation coefficient r(A:B) = 0.577 Degree of freedom n = 22 Significance level e = 0.16 % Before event
A: 1982.7.23. B: 2008.5.8. 1980 1985 1990 1995 2000 2005 Correlation coefficient (r)
asperities Pacific Plate
The point of this method is existence of “Preparing stage” • Distribution of inhomogeneous asperities • Quasi-static slipping • Stress redistribution
B: 2008.5.8. Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun 2007 2008 3.5 months before 4 days before r0 = 0.53 Correlation coefficient (r)
B: 2008.5.8. Correlation coefficient (r) Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb rB rA 2008 2009